Twice in a little over a month I've experience severe abdominal cramping and bloating that feels like an over abundance of gas just looming inside. This "gas" does not pass it just eventually after a day goes away (no burping/flatulence). The first time it woke me up, the second time in the middle of the afternoon.
It feels like my stomach muscles are being way over stretched and I actually have to unbutton my jeans for comfort because I'm so bloated. It hurts to walk, get in and out of a chair/car, and going up the stairs. It's hard to even stand up straight - and I've found that heat helps with the pain and discomfort.

Went to the doctors the first time and all that came back from testing was a UTI - which is most definitely not the case, just a coincidence. What could be causing this issue?

Have you seen your gynecologist recently and reported these symptoms to him/her?