Cramps only in the morning

I had my mirena fitted 3 weeks ago. I did not cramp until 2 weeks after insertion. The cramping is odd - it only happens an hour after I wake up and lasts on and off for 2-3 hours. It then subsides for the rest of the day.

I am getting worried that my IUD is not on the right place as the cramping starts and ends almost around the same time every day.

Has anyone else gone through this?