He hurts

I’ve been talking to this guy for a while now and I think things are moving in the direction of a serious relationship. So we have been having sex lately and the sex is so good but afterwards I’m always sore which is usually fine but I mean like SORE! Like throbbing and can’t sit for days. He lasts a long time and I think that might be why but is there any suggestions on how to reduce swelling or irritation??