Having trouble with sex positions

A little background. I’m 5’2” and my partner, he is 6’3” and this can make having sex difficult. We have done Missionary and cowgirl but can’t seem to do anything else. We tried doggy and reverse cowgirl but that didn’t work well. I think it might have to do with the fact that i get nervous and it makes it hard to put in so maybe I’m just to tense but idk. Do you think it’s our height difference. Does anyone have advice ???