I see you were H. Pylori negative, but I wonder what test you had for it... I've been struggling with similar symptoms and after a stool test came back negative for H. Pylori, I was sent for a GI work up. A biopsy during endoscopy came back positive for H. Pylori and I'm currently in the midst of treatment for it...
I've read that stool tests, often, come back with false negatives and blood tests only tell if you've had H. Pylori; they don't tell if you have a current infection. Supposedly, the breath test and biopsy are the most accurate.
There are also other bacterial over growths that can cause symptoms.
You might also try an elimination diet, starting with eliminating gluten, dairy, soy and sugar, as those are the most prevalent substances that people are sensitive to. You could be gluten sensitive without having celiac; you could be sensitive to, either, lactose or casein in dairy. Soy and sugar are, typically, big offenders. To do this, you eliminate all of those for a month, then try adding them back in, one at a time and see if they cause problems.
Get tested for Small Intestinal Bacterial Overgrowth (SIBO) via a lactulose breath test. The symptoms mimic yours exactly and you would either be high in hydrogen or methane bacteria. A major diet change will be required if you are positive (and a shift to a paleo diet that is grain free and mostly fruit free with the exception of blueberries here and there would be your bet bet.) I'm a Nutritionist and this is what I work with primarily