Mirena IUD cramps

I got my IUD 2 months ago, the process went smoothly And I only cramped that one day after the insertion. However I did bleed/spot every day up until last week. My boyfriend and I have unprotected sex regularly and I've experienced minor cramping after but nothing serious, it lasted a few minutes. But today after we had sex I got really bad cramps that had be bent over, crying and made me nauseous. It lasted for about an hour, now it just hurts a little when I flex my stomach. So this being said, has anyone experienced this before or have an idea of what it could've been ?