Cramps after sex

I just had sex with my boyfriend and now I have horrible cramps and my lower back hurts. We did our usual so nothing new and not hard either. Also i’m 4dpo but I don’t think that has to do with anything. Hurts when I orgasm too. Has this happened to anyone else and why does it happen 😭😭 it makes me not want to have sex, but I used to love it