What Causes Cramps During Sex?

hi i am 17yrs old and me and my boyfriend had sex the other day an we were it a position and had been having sex for abit and then something felt really really weird like he had pushed something up so i told him to stop and i stood up and started getting a cramp so i went and sat down on the toilet it hurt so bad i was going to tell him to take me to hospital i felt sick i got the shits a little bit i started sweating it was not good my stomach still feels weird its been giving me shit after i eat and starts a little cramping what should i do?