I need help with riding

Okay, so I’m relatively inexperienced and so is my boyfriend. (We were each others firsts and have only had sex a handful of times). Last time we had sex, I wanted to try being on top but MAN it is harder than it looks. Plus, I was trembling a lot because I was nervous.

How do I do a better job? Also, it’s gotten to where sex doesnt hurt at all and I was wondering what positions we could try other than missionary and me riding him.