Pain During Sex

Any doctors, nurses, or knowledgeable individuals on this topic.....?

Recently, I have been having pain during sex. It’s more of a deeper pelvic pain when the penis hits inside.

However, with one partner I have had sex with for about 3ish years now, there is no pain. But for this new partner, there is pain. I’m not sure if it is the shape of their penis’, or even if that has anything to do with it, but one causes pain and the other doesn’t.

How do you get this checked out? Where do you even go and what do you even ask for?

Any information would REALLY help! Thanks!