Pain!!

Ok so, I’m on birth control I have the IUD and I got it inserted on the 30th of October of this year and I don’t even feel it anymore, I have no pain no cramping, but yesterday me and my boyfriend had sex and it hurt sooooo bad, I started to cry. And I’ve had sex a week ago and it didn’t hurt at all, but it decided to hurt yesterday. So I don’t know what’s going on, and the sex wasn’t rough either it was sweet and passionate. So help what could be going on?