Plan b cramps

I had unprotected sex on march 25th (my 21st birthday 🙄🙈) I took plan b the next morning bc that happened to be my prime ovulation day. A week later, starting on march 30th, I experienced 4 days of a very light period with no cramping. I started my period yesterday (about 28 days later; my normal cycle) but the cramps are the worst I've ever had. I almost began crying during my lab class yesterday and I haven't slept more than 2 hours at a time due to them (it is now 4 am and I've given up on trying to sleep). Is this a one time thing? Or will my next few periods be this painful too? I normally have bad cramps but they're never THIS bad. It's also a lot heavier than normal.