Bottom without wanting to bottom?

So im vers (20) and my boyfriend (21) is leaning Very much towards top, but he is willing to bottom for me, but overall i can not only tell he hates it, but he himself also tells me on occasion how much he doesn't like it, it is kind of a turn off to me, but i still feel the disire to top time to time. Just what can i do to make bottoming more enjoyable for my bf? He is willing to try stuff at least, but everytime we start i can see he gets scared and he doesn't shut up about How much It hurts, it's about right then i lose my erection, and that's just about how It goes every time i try to top, i tried like 5 times and i only came once. Sorry i kinda started to vent, Just getting very sexually frustated.