Mirena Removed in September Cramping and Irregular Cycles

Hi so I had my mirena removed in September and I've had three periods since and my last one was only 5 days instead of 7 and was a week early. Now I'm about 8 days since my last period and I have been having a lot of cramping and pain. Before my IUD I would get a lot of ovarian cysts and I'm just wondering if maybe this what it is or if its something more serious I didn't get the cysts when I had the IUD. I'm cramping like a bad period and its radiating to my thighs, a lot of pressure in my uterus. Any advice???? Or anyone been through this?