Pain after sex

I've been with my guy for three years, and lately I've been feeling a little more sore or sensitive down there after having sex. I haven't talked to him about it yet, mainly because I don't know what is causing it. Even if its not that rough and I feel raw and almost kinda swollen from it, it most just uncomfortable then pain I guess. I don't know why this would suddenly start to happen, I've never had this problem before. Anyone else had this problem or know what's going on?