Why does Sex hurt me?

My boyfriend and I used to have sex more often, but my anxiety has since increased and now unfortunately I rarely ever have sex with him. But when we do, now it really hurts, but even before him when I had Sex with someone it never did. I get this deep pain in my lower abdomen. But once we’re done it stops. I’ve been on birth control for two years and only recently had it given me problems. Is this related? Is the pain from my anxiety making my body not prepared? I can not afford to see my doctor at the moment so I wanted some opinions for now.