I feel pain during sex, but i wonder maybe its because his thing isn't straight? its slightly curve pointing down?

Hi: It's probably less likely related to the penis, since even if it's a curvature problem, it should be the man experiencing this pain, not you. There are many different cause for pain during sex, including lack of lubrication, issues with the female reproductive organ, emotional factor causing vaginal tightness etc. You should see a doctor if you continue to have pain during sex.