Different Positions

Soo me and my boyfriend of two years just really started being sexually active, mostly because we’ve been long distance for the last year almost but now he’s back. We had sex once before he left, but now we do it pretty regularly since he’s back. We usually just do missionary, but I really want to try something different and he does to. So last night we tried with me on top but it hurt really bad, so we had to finish with missionary. Is there anyone else who’s had this problem? Or is it just a me thing? Any tips or tricks?