Please tell me they tested you for Celiac disease (the full panel and not just the single IgA Antigliadin test)? Pretty much everything you mentioned is either a condition associated with CD or something that CD is commonly misdiagnosed as... Of course, there are some ignorant doctors (like my GI) who still think you can't have constipation with CD (absolutely false).
I'm not saying that's necessarily what it is, but since CD is so common, and so commonly misdiagnosed, it's the first thing I think when someone has a list of issues and no diagnosis. And osteoporosis at such a young age?? Very common with Celiac.
One thing that's always a good idea is to ask your doctors for copies of your test results - blood work, EGD results, etc. Sometimes information that's in the results doesn't get communicated to the patient - doctors may ignore tests that come out "only a little" abnormal, or they may feel that "a little" inflammation isn't important enough to tell you about. Plus, you can't always assume that your doctor is fully familiar with everything in your file. They don't have time for that. Sometimes we're the only ones who will take the time to look at everything. Many of us have found interesting things when we look at our records.
GI disorders are just devilishly hard to diagnose, unfortunately - so many different conditions share overlapping symptoms, and the same condition can present with entirely different symptoms in different people. Add to that the fact that "tummy troubles" don't get a lot of sympathy from people who haven't experienced them, and it can get pretty frustrating. I think we've all shared your experience with the ER - unless you're dying or losing a limb, they don't do much for you. When I went., they were convinced my pain was due to pregnancy, no matter how many times I tried to explain to them that I'd had a D&C the day before (if I had been pregnant, a D&C would've terminated it). And that was at a good hospital.
Hope you find some answers, and please keep us posted!