What Causes Period Like Cramps While On Duphaston?

Hi doctor...i am 28 years old now.i was on infertility treatment for the last 1 year,all test done and both of us are absolutely fine without any problem, i did IUI on the 25 feb 2014(16 day) and taking duphaston 10mg 2 per day. Now i am having cramps that are similar as im gonna have my menses, Is this periods?Can i stop taking duphaston