Should I hang on or just let him go and be his friend?

I've been with my boyfriend for over a year and a half. I'm about to be 17 in two weeks and I've been with him since I was 15. He's 18 right now. For a while now...I've felt that I'm not as good of a gf and that he's a better bf. When you're in a serious relationship, your supposed to have the other person's back right? Well everytime i needed him or everytime i cried, he was there. I don't have a car and I'm not allowed to drive my stepmom's car all the time. It's only like twice a month that i get to drive on my own. My bf lived ten miles away and i can't just walk. Whenever he needs me, i can't always be there because i have no way to get there. And no, none of my friends are able to drive me. I know he really does love me and really does want to be with me. But how can I be with him if I can't even be there for him and be with him when he needs me. It's not fair for him. Should i hang onto him or just be his friend? I really do love him, I just can't keep this up.