This sexual problem I'm having is starting to ruin my life..?

Hey guys, I'm a twenty year old male and I have this huge problem that is destroying my self-esteem. It may seem like a gag question, but this is a serious issue of mine and I don't feel comfortable talking to anyone else about it so I'm turning to this forum in hopes of some answers... To keep it short, I can't seem to get an erection ONLY when its time for intercourse. Its been this way for a couple of years now. First time happened when I was with a girl after a party. I was tired, loopy from some booze, and took her upstairs because that's what my friends were doing with everyone else. We got naked, I couldn't get hard, and I ended up feeling humiliated. Recently I had a girlfriend and it took me a good three weeks to t to get some decent erections with her. At first I couldn't and BSed some

You have worded it wrong as it reads you can't get hard until you're ready for sex. That is perfect but I think you mean you can't get it up when you want to. I went through the failure you're experiencing for a long time and in the end it was down to nerves and inexperience with girls. .It was extremely embarrassing, but in my case it continued after marriage BUT not with my wife. I was very bad and played around many times, but the first times with any of them was the problem, so nerves came into it. Can only say be relaxed not tenses and don't be thinking of sex all the time. Good luck.