Seven Signs Your Spouse Is Cheating on You

How can you tell if your spouse is cheating? (Getty)

Veteran San Diego private investigator Patrick Schneemann, of Western Investigations, can describe what his company does in three simple words: "We catch cheaters."

Schneemann uses sophisticated surveillance equipment and other tools to gather evidence of infidelity. If you're worried your spouse is cheating, Schneeman suggests looking for these seven telltale signs.

1. Your spouse is overly protective of a cell phone. "They may password protect it. They may never let it (away from) their side. At nighttime they sleep with it. You know? That's a big sign," Schneemann said.

2. Your spouse frequently deletes text messages from his or her cell phone.

3. Your spouse is losing weight and working out more at the gym - it's a classic sign, Schneeman said, that still applies.

4. Another classic sign: The spouse claims to be working long hours.

5. Your spouse is spending large sums of money - more than he or she used to in the past.

6. He smells like perfume.

7. Something just doesn't feel right. "Trust your gut. Trust how you feel," Schneemann said. "Married couples are close…you're intimately close. You know each other. And (you) know when something's not right, when something's off in that relationship."

Watch the full story on the latest full episode of "20/20? online.