I think you need to sit down with your boyfriend and talk openly and honestly with him.
From what you have said, I get the feeling that he is a virgin, which is actually a plus point as it's nice that he hasn't been with anyone else before you. However, some guys think that it makes them sound silly to admit that for some reason.
It could be that although he loves you and wants to be with you, he doesn't feel ready for sex. If this is the case you should both wait, it is important that you are both ready to take such a huge step, especially where virginity is concerned.
There is a lot of pressure on a guy to 'perform', and when that pressure gets to them, things start to go a little 'soft'. The best thing to do when you think you are both ready is not to decide 'tonight is the night' but just see how it goes.
Spend time kissing and touching, being sweet with each other. When he is relaxed enough, it will happen for you and I am sure that he won't be so nervous the next time.
Losing virginity for a girl is a naturally big thing, but there is a heck of a lot of pressure on the guy too and that often goes unnoticed.