Thanks for writing to HCM!
I have gone through your question carefully and I really understand your problem.
If I had been in your place I would sit and talk to him and ask for the reason for his behavior (as you didn't mention anything on this in question). Knowing the reason only can help to rectify the problem. I would not treat him with any medicine until I know why he does like this.
Does he performs sufficiently when you have sex? There are some major questions which will clarify and rule out many causes. Such behavior can be due to many reasons from
depression, to just lack of interest to any organic problem....It is not clear from the question.
If I had been your doctor, I would like to know his mood otherwise during the day, how is his behavior.
You have been handling too much of it alone, I would advice you to go to a specialist or talk to some physician alteast regarding this. I'm sure things will become better.
hope it helps you, please feel free to ask further.
Dr. Manisha Gopal