The fact that you feel you are headed for disaster worries me as I'm sure it does you. I strongly suggest that you openly address the issues dividing you now. I sense that your drop in sexual desire has more to do with your fear of rejection than a disinterest in sex or your husband. You need to be courageous and confront the distance between you now so that you can reconnect to your husband and take advantage of the youth and vitality you both enjoy. Make sure your husband knows how you feel and if he won't seek help, do so yourself.
QUESTION: My husband was diagnosed over 2 years ago with a testosterone deficiency and was prescribed a shot every 2 weeks. However, he does not get his shot when he should and now has not gotten it in over 4 months and does not care to. He says it does not help him any. In the meantime, sex with him is a 1 minute thing in which I do all the work as he is too tired. I do not get affection from him either. Over the summer we had an experience with another couple in which my husband interacted with another woman and showed her affection and foreplay. This completely confused me as he does not act like that with me. My question is: how do I motivate him to get his shot and take care of himself so we can have a loving relationship?
ANSWER: Start by asking him to read The Sex-Starved Marriage. So often, people with low sexual desire do not realize the hurt their spouses because of their disinterest in being sexual. The book will help him understand the impact of his low sexual desire on you and your feelings.
You mention that your husband seemed interested in another woman. Oftentimes people with low levels of testosterone feel turned on by the newness of someone other than a spouse. Unfortunately, extra-marital relationships and sound marriages generally do not go hand in hand. However, there might be something to be learned from that experience. Is it possible that sex with your husband had become very routine and unexciting for him? Are there ways you both could liven things up so he feels newness and novelty with you? Have you talked openly about what might be missing for him and what is missing for you?
Above and beyond this, it appears that your husband may be experiencing a sexual dysfunction where he ejaculates too quickly. Perhaps he is embarrassed by this and avoids sex because of his sense of failure. The good news though, is that there is much that you both can do to learn techniques for overcoming this problem. A good sex therapist can help him to gain control and last longer during lovemaking. You will learn what you can do differently to help him. If he's too ashamed to go to a sex therapist, there are many good books on the subject.
But even if he can't maintain an erection, there are many things he can do to help you feel sexy again. You should coach him as to what feels good to you, how he should touch you, what he should say to you. And let him know that you will appreciate any and all effort to connect with you physically even if you don't end up having sex. That will take the pressure off him and he might relax and show more interest in you.