After just briefly reading these forums, I realized I'm far from alone. But let me get this off my chest since its been bothering me. I was with a girl for 4 years, when we first started being intimate, I remember having trouble getting an erection at all, which I attributed to stage fright and it only lasted about a week or so, after that I had no problems, EVER. This girl and i ended up getting engaged and about 8 months after our engagement I caught her cheating on me which ended that relationship... needless to say. Now to the current problem. I'm 23 years old, a healthy active guy. I've been seeing a new girl now for about 3 months and when we are messing around I have no trouble getting erect at all. The problems start either when I take my pants off or about a minute after insertion. Its no that I'm not attracted to her, as a matter of fact i'm more attracted to her than I've ever been to any girl in the past. This happens i'd say about 75% of the time. I can't figure it out. She obviously notices this and gets really upset because naturally she thinks its her. I insist that it isn't, but I feel like everytime she gets upset about it, it puts more pressure on me. I have no trouble getting aroused any other time, like when I masturbate, and I still wake up with an erection after REM sleep. I am trying to figure out if I'm psyching myself out or what. It is getting very frustrating because I really like this girl and I feel like this is ruining our relationship. Any advice at all?
Part of this is the vicious circle of worrying that you wont perform therefore you dont, but also underlying this is the fact that despite everything else not being problem this girl is special to you. This subconciously uncovers things that you are not aware of, but your penis is. It could be anything from not wanting to hurt her (ie protecting her), to not wanting her to get pregnant. Just the fact that you care for her a lot is part of the cause.
To help here, move back a few steps, back to just being comfortable with each other, hugging, kissing but not having sex. Then move on to gently exploring each others bodies, but not going for sex. Work on this so you even masturbate each other or do oral, but do not attempt to penetrate.
Over a period of time, you will have learned to trust each other in what each other wants and likes, and hopefully you will also be comfortable to try to penetrate her. You must by this stage have got any worries about performance out of your head, so that this is not a factor here so that you two can be comfoprtable and just relax and end up having sex with no pressure.