I am a 21-year old male and have been experiencing weak erections for quite a while. About three years ago, when I first started having sex, I used to have a real hard time getting it up, but I attributed it mostly to nervousness and my then-girlfriend's lack of empathy on the issue. I finally resorted to viagra for a couple of times but the relationship dissolved anyway. I had another failed attempt at sex one year later with another girl.
Anyway, I'm in a relationship now, with a considerably more understanding person who's into me, but, strangely enough, I still experience difficulty performing. It's not that I don't get erections, but they are not hard enough to sustain intercourse. I've managed to have sex a couple of times using viagra again, but the side-effects are just too much to handle (palpitations, muscular and back aches etc). It lead me to think that I might have some cardiovascular problems, but I went to a cardiologist and had a physical and ECG and he found no pathology whatsoever. I monitor my blood pressure and it's within normal range; my pulse is a little elevated but not within pathological range. I also went to a sexologist and had a penile Doppler and nervous stimulation test to exclude any organic conditions. My blood sugar and fat levels are also within normal range.
I've talked to my girlfriend about it and while she's willing to help me work through this, I still don't feel at ease and have continued to experience this problem. On the few occasions we've had sex I also happened to lose the erection during intercourse. I've been doing a lot of reading on the topic recently and I've found a lot of tips on the "Losing erection during sex" thread on this website (I'm a skeptic about most of them but they're worth a shot). I've taken up Kegel exercises for a couple of days, I'll try to get some more sleep and start exercising, and I'm even considering therapy. Some people have suggested hypnotherapy, but I have serious doubts about its scientific merits.
While I do think part of the problem is psychological I also think there has to be some extra factor involved.
Are there any of you who face(d) the same problem and, if so, how did you overcome it? I would also like to hear some input from someone with medical training, since this is a complex condition with no simple answers. I don't want to sound rude, but please don't post advice like "just try to relax", "be comfortable and take it easy" or other such tautologies which aren't any help. Thank you in advance.