Well, I guess he shouldn't have been doing it then.
You know, I mean, if he felt that guilty. He felt he was doing something wrong (even though he really wanted to) and he went ahead and did it anyway. The performance problems he experienced was his conscience overriding his libido. A good thing, actually. This doesn't surprise me much after hearing that things "got weird" between you all.
At the risk of being politically incorrect, could you tell me what your ages are? Or age range, if you prefer? 25-30? 18-25? Under 18? I could be wrong, but I'm guessing you're not over 30...