splitting/tearing during sex

So after sex it's always a bit painful for me, and occasionally a small amount of blood on toilet paper. I can feel that the bottom opening of my vagina has a small tear/split and it takes a while to heal, meaning if I try and have sex again a few days after it is painful.
I don't consider my partner to be "massive" and we don't have really rough sex or anything.
Is it me? Or is this normal?
Can anyone suggest anything to prevent it, it makes sex a bit negative for me.