Unexplained Vomiting = Bad Gallbladder??

I have been vomiting, usually without nausea, for nine years. There are weeks when I throw up every day, sometimes 3 to 4 (or more) times a day. There are other times when I won't vomit for 2 weeks. It doesn’t change according to my diet. The vomiting usually consists of a simple back-up of food; I don’t get nauseated, I just throw up. I don't want to be too graphic, but it usually consists of food with a lot of acid and bile. I’ve gotten really good at controlling it, so I don't get sick in inappropriate places, and sometimes I can even force myself to keep it down. Sometimes, however, it turns into violent, projectile vomiting; I have been to the emergency room three times in the last four years because i've thrown up so hard i've torn my esophagus. The last time was just last week, and I was throwing up brown acid and bile. The pain in my stomach (just below my ribs in the center and right side) and in my back were worse than the vomiting.
I have also been constipated pretty much my entire life; when i’m not constipated, I have diarrhea. I have had at least three endoscopies, two colonoscopies, half a dozen ultrasounds, a gastric emptying test, several ct scans, and at least two mri's. I’m sure i’ve forgotten more than I remember; every new doctor I see wants to put me through the same tests that the last doctor did. All of the tests come back normal. The gastric emptying showed a 24% ejection fraction, but i’m not sure what that means. One doctor suggested gerd, gastric dysmotility, and ibs; the others seem to be content with ibs. I have fibromyalgia, and once they finally diagnosed that (after four years,) the docs were quick to blame all of my problems on the fibro.
My newest gastroenterologist ordered a hida scan, which is scheduled for next week, but he’s the first one (after nine years and about 100 doctors) to suggest that it could be my gallbladder. A ct scan and an ultrasound both showed that I don’t have gallstones, and many of the sites i’ve seen online seem to suggest that you can’t have gallbladder problems unless you have stones. The more I research the gallbladder, however, the more I feel like it could be my problem. I’m trying not to get my hopes up, because every test I have comes back normal, but do my symptoms sound like they could be caused by a bad gallbladder? I can’t help but hope that if they’ll take my gallbladder out that my stomach problems will disappear, or at least dissipate. What do you think?

(i want to apologize for the capitalization problems; it won't captialize in the middle of a sentence!!)