being on top

Ok ladies, I need some advice. I tried being on top for the first time the other day and it did not go well. I  ended up bending his dick in an uncomfortable way and we ended up needing to take a break before we could even go to another position. What am I doing wrong? I didnt feel like I was in an extremely angled position, but I was wrong. What can I do to make it better? Help please!