Nervous about having sex...

I've been with my boyfriend for 7 months now. I love him, we're both happy. It's a little embarrassing and I'm really self conscious about it but I'm 18 and still a virgin. He's both much older and much more experienced in bed than me. I want to have sex with him and share that experience with him but as much as I would love to have a baby in the future, I am not at a point in my life where I can have a baby. And every time we go to do it I freeze up, despite having protection ready to go, I'm too nervous to actually do the deed and I don't know why. I feel like I'm letting him down. We talk about it and he tries to reassure me (he is never pressuring or forceful) but I just can't bring myself to do it. How do I just let go and do it and accept it and be happy???