Pain during sex

I’m 18 yes old and have been having sex with the same guy for about 4 years. I’ve never been active with anyone else and never had an issue during sex. But for the past couple months it’s been starting to hurt really bad. At first it was a yeast infection then it went back to normal. Then it started to burn and itch and got treated for a uti and the burning and itching went away but it’s hurting really bad during sex. It doesn’t hurt when I pee or when I’m just going about my day. It only starts to hurt and sting when I have sex, does anyone have any ideas as to why or how to make it better??