Cramping after sex

Hattie • Student from Oxford 🌲 here to help w any questions 🍒 stop slut shaming
The last three times I've had sex which have been after I've come off of my my recent period I've got awful cramps which are so so painful. It happens straight after sex and for about two hours. I have a coil but this has never happened before and I've been having sex for a while so what is happening??