My first thought was Celiac Disease as well because that is what happened to me. Mine hit more gradually though but was triggered by my c-sections. If I were you, I'd try going on a gluten-free diet since you have some time before your surgery. Blood tests can give false negatives and they can only test for certain proteins whereas they are finding that there are actually many other proteins that may be bothersome to people.
At one point, I had tried going GF but didn't notice a change. Turns out my body was too overwhelmed because I have multiple allergies so I wasn't getting any relief by just going GF.
If you do GF, you have to be really diligent about ferreting out the gluten, otherwise your body may still react to small amounts that you do ingest without knowing it. Also, casein can be another culprit as it is sometimes mistaken by the body to be gluten.
I wish that tests were more accurate but if it's dietary, it will be trial and error and it will take some time and dedication :(
If I were you, if it ends up not being adhesions, I would go to an ND to help you figure out what's going on in your body. I love mine because she actually listens!
Hope you feel better soon!