It’s because you have rough sex several times a day. Also, if you’re well endowed like a porn star, you're probably hitting her cervix repeatedly, which really hurts after a while. I know from experience.
My advice is, tone down the rough sex. I find I can have sex once everyday, given proper natural (not artificial) lubrication, which means I want to have sex, not just the guy, and also if the sex is not rough or so deep that it hits my cervix. Be gentle and do more foreplay and cut down on the porn antics. I feel bad for this poor girl. Please don’t pressure her to have sex with yo