What Causes Stomach Pain With Diarrhea During Periods?

Hello I was prescribed Utolvan to delay my period whilst on holiday. This stopped by period and I finally recieved the period a few days after I got back home. The period was shorter and I have been having a dull pain in my right side underneath my belly button and have had diarroha since, also feel a little light headed now and again. I am 27, 5 6 and average weight and build. Thank you