Sore after sex

Hello all!

Do you experience soreness after sex? My SO is the only one I've ever had sex with, so I'm unsure how it's supposed to feel afterward. In the moment, everything is good, and he gives me the best orgasms. Afterwards, when we cuddle I sometimes feel crampy. The next day or two im always pretty sore inside... It almost feels like muscle soreness after a really hard workout! Is this normal? We've only had sex four times.. So I'm wondering if I'm still just not used to it? I know he's said he is aggressive and a bit rough when we're having sex, but it doesn't hurt or anything when we are actually having sex-- is it possible to just feel the pain after? Do you have any suggestions to lessen the pain?