Is the door locked? Is the stove off? What about the alarm: Is it set? These are questions many of us ask ourselves every day. And once we check, the thoughts subside.
But for people who suffer from obsessive compulsive disorder, these thoughts become obsessions, which haunt them night and day, and can lead to sometimes bizarre rituals that start to control their lives.
OCD is a devastating illness that affects about 5 million Americans, and about 1 million are children, according to the OC Foundation. People living with OCD are not only tortured by obsessions and repetitive rituals but by recurrent and persistent unwanted thoughts and images. It's a crippling disease that is often misunderstood.
"Primetime" followed children who are battling OCD and their families from the doctor's office to their homesas they attempted to overcome the stigmas associated with the disorder and reclaim their lives.
For 15-year-old Bridget of New Jersey, her personal battle was about getting back home.
Though Bridget looked like a typical teenager on the outside, inside she wrestled to break free from the unbearable fear that her own family was somehow contaminated and could infect her.
Click here for more information on how to treat obsessive compulsive disorders
"Think about it as being something that's dirty -- radiation or something like that. It spreads," explained Allen Weg, a licensed psychologist and the founder and director of Stress Anxiety Services of New Jersey and Pennsylvania. "And so when this thing touches the thing that's contaminated, then that thing, that new thing becomes contaminated."
But things weren't always that way for Bridget, a happy child who loved to swim and enjoyed being around her family. Enrolled in the gifted program and a star student in school, she brought much pride to her parents.
Bridget's first signs of compulsive behavior came at age 11, with what her mother, Karen, described as a need to be perfect in school.
"Everything had to be a 100, or she had to know every spelling word," Karen said. "Then all of a sudden she started to notice that her books had to be in a certain place, and she didn't want certain things touched."
CLICK HERE to see photos of kids battling obsessive compulsive disorder.
Sixth grade was a struggle for Bridget, but she said she believed things were getting better, and she was able to stop taking medication in eighth grade.
"Then [in] eighth grade, miraculously, it was pretty much better. So I stopped taking my medicine, I stopped going to the therapist. And then over the summer between eighth grade and freshman year, that's when this came up," Bridget told ABC News.
When Bridget entered high school, her OCD returned, morphing into a more severe form. She feared that her family was contaminated, which prevented her own parents from touching her.
Karen struggled to find her daughter the right help, taking her to see a therapist in the fall of 2008. But four months into treatment, Bridget showed no signs of getting better, and it was becoming harder and harder for her to be around her family.
In September 2008, because the constant fear of her family consumed her, Bridget had to move out of her house and in with her grandmother. The move was especially trying on her mother, Karen, who drove between her home in Aberdeen, N.J., to Bridget's grandmother's home, which was nearly an hour away.
Desperate for results, Karen switched Bridget's therapist, bringing her to see Weg, who introduced Bridget to Exposure and Response Prevention Therapy, or ERPT, a type of therapy in which a patient is exposed to his or her fears in order to desensitize them until they are no longer all-consuming. ABC News was given rare access inside the treatment room.
In each session, Bridget struggled to get closer and closer to her mother -- as the two practiced the seemingly simple act of sitting on the same couch as one another at home. For Karen, that meant traveling more than 18,000 miles over the course of six months between her family's homes to get closer to Bridget.
"During ... her school day I would come home, do what I needed to do; go pick her up, bring her back to ... my mother's," Karen said. "Then we would get together. We would go to swim, or she would do her things.
"If she was at swim, I would drive her to swim, and then, again, come back home, try to see [my son] Mark and my husband for a little; go pick her up and ... bring her back," she added. "And that was kind of ... our cycle for many months."
Bridget's OCD fears began to attack her swim cap and then her swim bag. Her growing fears combined with the extensive cycle of transportation to treat her OCD caused Bridget to give up the sport she loved so much.
Karen had to divide her time among helping Bridget get well, caring for her sons and working, which she said was often excruciating.
Like Karen, many parents with children who battle OCD wonder: Was it something I did? Why my child?
"It's very difficult for parents to come in and not believe that they've done something wrong, that their kid has all these fears and these strange and bizarre fears," Weg said.
Diane LeClair asked herself the same questions when her 13-year-old daughter, Michelle, was diagnosed with OCD in September 2008. Michelle feared that other students were contaminated, keeping her from going to school or any public place where she has seen her classmates.
Michelle told ABC News how she wouldn't let her mother shop in stores nearby for basic household needs.
"We had to go like hours away just to go get like a pair of pants or get cleaning supplies ... to wash the washer, because everything around here was contaminated," Michelle said. "All the stores were [contaminated] because the kids from school had been there."
Her crippling fear kept her isolated at home. At her worst, during the fall and winter of 2008, Michelle's laundry had to be done separately from the rest of the family's. One laundry cycle often wasn't enough to convince Michelle her clothes were clean. Even the washer had to be washed.
Michelle's compulsion forced her to shower incessantly in blistering hot water. Even the allure of a brand new puppy couldn't get Michelle out of the shower.
"We were going to go get him puppy toys and take him to the store and she was so excited that whole day," Diane LeClair said. "And after an hour in the shower, I'm like, 'We need to leave if you want to go,' and she couldn't do it.
"I shut the water off, I pulled her out of the shower, and she [screamed], 'Don't touch me, don't touch me,' and ... just sat on the floor, rocked and cried," she added.
Diane LeClair quit her job as a teacher to work full time helping Michelle fight OCD. When school became too much to bear, Michelle took a leave of absence, turning to home-schooling.
In fall 2008, Michelle's fear of being dirty became all consuming and she plunged into depression.
"I became suicidal because I couldn't touch anything, and when you can't really touch anything, you can't do anything. You can't enjoy anything, so there wasn't really a point in living anymore," Michelle said.
Michelle worked with Weg in extensive therapy to manage her OCD. Outside Weg's office, Diane LeClair became her daughter's OCD coach, coaxing Michelle to get back to school one class at a time.
Parents such as LeClair invest a lot of time and money in treatment. Therapy for OCD is expensive, and insurance often does not cover the costs, leaving many families on their own.
Just ask John and Margaret Decorso, whose son Rocco was diagnosed with OCD and Tourette's -- two conditions that often are closely linked -- when he was 8 years old.
Fear of "what if" consumed Rocco, from the fear of getting sick to the fear of what could happen when he left for school. Every day, he begged his mother to repeat herself, to keep reassuring him that everything would be OK, which can tear down even the most loving moms.
"Sometimes we're like, 'Get over it, knock it off already!' said his mother, Margaret.
Signs that something was wrong came when Rocco was 5 years old, and he talked about wanting to die.
"He says, 'I can't live like this no more,'" Rocco's father John said, holding back tears. "Coming from a 6-year-old saying, 'I can't live like this. I want to live with God,' you know., 'Don't worry, Mom and Dad, I'll look down after you.' That's tough."
After seeing doctor after doctor, they eventually found Weg, who was able to offer treatment options for the struggling family.
OCD is a chronic disorder that lives inside people forever. Though there's no cure, but Weg said it can be silenced if you know how to manage it.
"We don't use the word 'cure' for OCD, 'cause that implies that you have OCD and then you end up not having OCD -- and, for the most part, that's not really the case," he told ABC News. "The vast majority of people that I work with end up being able to manage their OCD to the point that they're aware of it to a certain degree every single day."