Intense pain

I have had the mirena IUD for a little over 6 months now. The last week or two I’ve been having really intense pain in my uterus. It’s bearable but definitely intense. Sometimes I need to sit down and breathe through it. I just don’t know whatsbe considered normal and what isn’t. My doctor didn’t really go over the side effects. I also didn’t ask I just figured he would have informed me (guess not) but up until the last few weeks everything had been pretty great.