Well, a doctor cannot say any more for his patient even if he knew, otherwise he would break confidentiality, no matter what the subject at hand is.
It is pretty obvious that the time has come to think both of you what's going wrong with your relationship and if you can keep going that way or not, and if not then what can/should be done.
Good luck.
I do have a very strong gut feeling that he tried really that he did cheat and when I got this same gut feeling before about this same thing I was right. He has not talked about being out or why he stayed at the bar after his friends left and I have not said anything yet either ! But I plan to this weekend we always talk on saturday nights when he gets home from band practice so I will see what he says then! Plus if he's been drinking he always tells on his self. And he has talked to his doctor about the problem he's been having getting an erection and the doctor told him it was his life style my husband told the doctor that I thought he was cheating and we had problems and the doc asked him if he was and he said no but he didn't tell him that he had tried to. but I go to the same doctor and I told him everything and he feels like I feel .
> How can I tell if he tried to cheat or did cheat?
You can't. You have just strong indications that something goes on (you already catched him telling you lies, which is serious in a couple) and you need to keep your eyes and ears wide open.
Besides the socio-psychological aspects, did he take some medical advice on the possible conditions that could lead to the loss of his erections?