riding?

My boyfriend and I have been dating for 3 months and I lost my virginity to him 2 months ago. He’s a lot more experienced than me and he has been really patient and supportive with everything, especially sex. I am too scared of embarrassing myself on top, or really doing anything for him, and he does all the work generally. Sometimes he’ll sit up and i’ll grind on his dick which is fine but I can tell he wants me to do more for him even though he says it’s okay if I don’t. I have too much of a gag reflex to give a bj but I could ride if I knew how. We generally can only have sex in a car because that’s the only time that we can honestly so keep that in mind. His car is big but it is still not the same as a bed. Any tips for not getting tired, doing it right, etc? Also how can I gain confidence? It isn’t my body, it’s that i’m not confident in my sexual abilities. Thank you ladies :)