Pain during sex!

Okay so I have this problem that when my SO and I are having sex. We will be about 5 minutes in and the bottom of my vag hurts really bad to the point where I have to have him stop and reposition himself. If he's to far down it feels like he's ripping the skin at the bottom of my vag, and sometimes he does.. We also use lube and it still doesn't help. I don't understand why this happens and it's really ruining my sex life with him.. Please help!