I think too much during sex, not enjoying it! Help?

I'm male and 19 years old. My first sexual experience wasn't long ago, I was 18 and she were 17. She didn't know I were a virgin at the time, and she expected a lot from me. When it came down to having sex, I put a condom on and lost my erection. And felt a complete fool. I was so embarrassed, my confidence hit rock bottom. In the end I just pleasured her orally and that was it. Not long after that day I explained I were a virgin. 2 days later she finished with me. So I was kinda heart broken. I finally lost my Virginity to a girl 3 months back. Once again she didn't know I were a virgin at the time. I put a condom on and lost my erection. Twice this had happened, made things worse. I blamed the condom, when really it was just nerves and pressure. However she said take the condom off and we had intercourse. She took the lead, therefore she figured out I were a virgin herself. 2 days later, she finished with me too. Started hating on women at this time. But I have recently been seeing a lovely girl and I explained all this to her. So she knows I am not experienced. We had sex for the first time yesterday, with a condom. And it did work for a bit, but I was thinking too much. About pleasing her, wandering if she is enjoying it and what not. I also expected a lot from vaginal sex but its not what I thought it would be. I expected to ejaculate within seconds/minutes. It just didn't happen. I was actually having problems feeling anything to be honest (even though I am a goooood size down below). My mind was on all this too much and I started to lose my erection and I pulled out. That was it for yesterday. And she kept telling me to relax, lovely girl she is but the sex thing is getting to me now. I think with vaginal sex I expected it to be amazing from the word go, and within seconds be having the time of my life. I guess I just have to keep at it until I do ejaculate?