Nervous?

Does he use pornography? I was with a guy who could not perform with me(only in his 20's) as he was so used to masturbating to pornography and wasn't able to get excited enough with me. He was addicted to more extreme type sexual situations like girls together and orgies and just one girl wasn't enough. He went to his doctor and instead of suggesting therapy or quitting viewing porn, he gave him viagra. This still didn't work too well. I'm sure that you can overcome the problem, but maybe you can gently ask if he is a porn user?
I had to break up with my guy over this as he never was able to have sex with me but I found out that he was using porn every day!
It's an increasing problem. I am only 24 and most of the guys i know look at it constantly.

Possibly!

According to the Kinsey Institute Confidential, "...very often in young men, erection problems are often influenced by performance anxiety (concern about performing a certain way during sex, giving your partner an orgasm, lasting long enough, or being able to get or maintain an erection). When younger men have erection problems, other types of anxiety (like concerns about relationship problems, upcoming exams, work, family problems, etc.) may cause problems too."

"Some men find that focusing on sex play that is less genital focused (e.g., making out, massages, bathing together, erotic touching) makes it easier to enjoy sexual pleasure and to maintain erections."

Does this help?