No Positive OPKs but having pain???!?

Hi ladies!!
I have called my doctor, nurse on call, and read everything I can and I still can't figure out what's wrong with me!!!!!
To get right to it. I MMC on 6/3 and went through one good cycle that was only 1 or 2 days off from what I would have expected. We planned on trying for our rainbow baby this month!
But ever since AF ended I've been getting pain in only what I can describe as my uterus. It feels extremely similar to how I felt when I was pregnant. Slight pain if I'm moving around too much and almost constant pressure. 
It's this cruel feeling because I'm not getting positive OPKs and I took 2 pregnancy tests and those were duds too. Today is supposed to be my prime BD day!! 
WTF!!! I'm so confused and I can't find anything to calm my nerves. Every negative is making me cry!
So sorry this was such a long post! I'm just so worried. Any information you ladies have would be extremely appreciated! I don't know where else to turn except going in for another extremely uncomfortable ultrasound. 
Thank you all so much! All my love and BABYDUST!!!