It hurts!!

So I know this is weird but the pain comes and goes and it's practically ruining my sex life!! (IT DOES NOT HAPPEN EVERYTIME!) Sometimes when my SO and I have sex it'll hurt/burn really bad to the point we have to stop. It feels like he's rubbed me raw with the friction but I'm not sure that's the actual problem. We hadn't had sex for a week and when we did as soon as he penetrated me it started to burn and hurt. I've been tested for STDs and STIs which came back negative. I don't believe I have an infection as I was tested about a month ago and I don't think it's a lubrication problem but it's possible but it doesn't happen every time and it makes me not want to have sex. And after we're done it'll keep burning and when I pee afterwards it feels horrible! Like I have to hold me breath to pee because it hurts so bad. Now I know it isn't normal but what could it be? Has anyone else experienced this? Please help!!

UPDATE

We do not use condoms, unless I'm on my period and it does rub me raw sometimes but not as bad without. Also, I noticed that if he makes me cum it tends to dry me out and makes me raw but that doesn't happen every time either.