I don't know how old you are, but things can change (usually for the better) as you get older. I always orgasmed easily, but not through penetration until I was about 41. It was with a VWE partner, so I assumed it was a one-off, but my next partner was smaller and I still cum every time through penetration, and have with every partner since. I also now come just from nipple play, and the handful of times I've done it (only lost my A cherry in January) through anal as well.
I think a lot of it is psychological, about feeling relaxed, not bothered what you look like, just letting your body go etc.