pain during sex, every time! HELP

Chloe • Mum to 2 boys
I've come to realise that I may have something going on down there. At first I thought it was normal but it isn't stopping. Every time i have sex it hurts, especially in the beginning, it's almost unbearable and I want to stop. It feels like a stinging, tearing pain and it really, really hurts, at first I thought it happened because it was my first time but now my partner and I have had sex around 20 times. We both lost our v cards to eachother in February of this year and although that wasn't long we do know what we are doing, as far as I know I'm healthy down there, there's enough foreplay and I'm lubricated enough, he's of an average size, there's a possibility I could be quite "tight" I suppose but I really just want to be able to enjoy sex and I can't with this pain. I really need advice. Please help!