Pain in lower uterus

Kimberly
So my husband and I have been TTC and AF is supposed to be here in 5 days. Just a while ago I got up from the couch to go lay in bed and had a sharp/dull pain in my left lower side of my uterus. I dont think I'm pregnant cause I have no symptoms. But, idk. It comes and goes. Not excruciating but hurts a bit. Any ideas?? May be gas too. Idk I feel like I have to fart but why would I be getting the pain in my uterus??