17 and can't maintain an erection!?

I'm 17 and about a year ago when I had my first time with a girl I couldn't get a proper erection. Then I went away for the summer and didnt have sex for 2 months (masturbation seemed fine) and the first time I had sex I could maintain an erection for atleast 30 mins. But then every time after that, there's been some problems trying to maintain an erection, or get one at all. For instance before sex when I'd still have jeans on, I would get a good erection coz I was excited, but then when she would give me a ******* or a handjob, my penis would go slightly softer and then as soon as I put the condom on It would get noticeably softer. And throughout the whole time I'd be saying to myself 'dont give up on me!!' and that is probably why I couldn't keep it up. My thoughts are that it's nerves, and the fact that I didn't like the girl anymore after i got back frm the summer vacation, and I didn't find her that sexually appealing. Plus I watch quite alot of porn and so the girls in real life arent as sexually appealing. Sometimes in the shower I can't keep an erection for long, but I can climax eventually. However I still get morning erections almost every morning I wake up which I hear is a good sign.

[kleemas]

I think ur just thinking about it to much, sometimes i will have a nice erection going then when i get up and put a condom on it starts to dimper a little, but i just put it in her and start going and in like 2-3 secs BAM its back to full force.

Try to avoid thinking about it too much just think about ur partner and love and what not. also u could lay off the porn and masturbation for awhile, do this for like a week or two and ull have erections all the time.

not being sexually attracted to someone can play a role as well.

u shouldnt really be comparing porn stars to "real life" women.