Pressure in uterus?

Hey! So the last 2 days I've been having a tiny bit of spotting (like brownish color - and very little) so I assumed my period is coming. It's been irregular since having Jaydess inserted. Well tonight after my bf and I had sex, I've been having bad cramps, more like gassy/bloated feeling, but in my uterus. They've been on and off, but it seriously feels like a bloating of my uterus. It's really uncomfortable. I've taken antigas pills incase that's the problem, and I've felt to find the strings / no point sticking out. And all that is fine. He said there was a tiny bit of blood, but I've had no other bleeding. I'm just paranoid after I've already had one IUD (the mirena) reject.