Pain while having sex ?

Nancy
Hey guys so my fiance & I have been together for 3 1/2 years & always have alot of sex lol but yesterday when I was on top it felt like rather he was too deep or something that it hurt when he'd push me back for more penetration . This is so weird because we honestly have alot of sex & this has neeeveeer happened before lol sorry if its too much info but just wondering what it might be ?
P.S. Im 21 & trying to conceive but havent been able to for about a year now && we've never used any type of protection besides just condoms when we were first dating ofcourse .
Anything helps thannks !