Pain during sex?!

I lost my virginity and have been having sex with my boyfriend of 5 months tomorrow for the last two months basically. I have been getting pain when he goes too deep, almost as if there's air pushing my guts in or something. I read online that it could be him hitting my cervix, and that for some women it could feel like getting hit in the balls (if that's what it feels like I will be more sincere next time he gets it), but it just won't stop. He could go so far and then on little tiny movement and it's like the needle that hit the bomb set off the explosion. Sometimes we have to stop. Can anyone please give a reasonable explanation as to why it is hurting and why it isn't stopping?