I've had some similar gastrointestinal problems before. I took all gluten, dariy, artificial sweeteners, and red meat out of my diet and started on probiotics and a ginger supplement and within 8 weeks my problems vanished. Well just my gastro issues. And make sure to drink plenty water. Hope this helps!
Had the same for 15 months, as well as the tests, I even cut out all starches and sugars, and finally got diagnosed with enterobiasis, a pinworm infection.
Since I take a deworm, my weight has come back and I am nearly complete pain free. Just have to fight with nausea every now and then.
You can try to get tested, ask for a scotch tape test. Pinworms rarely show up in stool samples.
I recommend that you look into endometriosis. Endo gets on the bowel all the time. If you can find an endo specialist, a gen ob/gyn does not know enough about endo to diagnose and properly treat it. To find a specialist near you contact the endo association:
I hope this helps,
I forgot to also say that your are right, the test for celiac is not very sensitive. And some people also have "normal" endoscopies but still are intolerant of gluten. So you can always take it out and see how you feel. But do not forget to keep endo in the back of your mind because at least 80% of women w/endo have issues with gluten.
Could be a gluten issue, or another an allergy/intolerance to another food. The standard approach is an elimination diet. The celiac tests are good, but there are several reasons that false negatives occur. I went through years of problems like you're describing, and eliminating gluten, dairy, and eggs basically resolved them all.
Endo is another possible explanation, though you'd probably also notice symptoms related to your period. Diagnosing endo can be tricky; my ex-wife went through it, and it was only after a burst ovarian cyst leading to endoscopy to remove the damaged ovary that the endo was confirmed. She was successfully treated by a specialist we found through the above-mentioned Endometriosis Assn.
There are, of course, other possibilities, too numerous to mention. If dietary changes don't help and endo is ruled out, you'll have to work with your PCP to figure what explains your symptoms. Good luck.