Your ejection fraction is too high and it is what could be causing the discomfort.
Hopefully, you're following a low fat diet. If not, try it to see if it helps at all. Another factor that can effect the gallbladder in some is if they have celiac disease - a problem with the ingestion of gluten. For whatever reason, that specific food sensitivity can cause an over-active GB.
If you're taking any form of hormones, you might want to consider speaking with your doc and seeing if you can substitute. There are people on birth control pills that find that those pills can impact the GB adversely.
In some with pain caused by spasms of the common bile duct or sphincter of Oddi, the use of something like bentyl might tamp down the discomfort. It's by no means a cure, but you might want to discuss it with your doc.
I agree with CalGal. I think your doctors are being lazy. They need to test you for Celiac disease.
For possible quick improvement, see if stopping dairy, especially milk, helps your symptoms. If it is Celiac disease, dairy is likely to give you trouble. Don't stop gluten until you have had blood tests for Celiac. Once you have been tested, you may want to try a test of stopping foods containing gluten, because even if you are negative for Celiac, you could have a gluten sensitivity. It's not as life-threatening as Celiac disease.
Definitely cut out on bad fats, fried food, fast food. You could try taking Metamucil (which is gluten-free if you get the name brand) at night. My boyfriend takes 5 capsules at night and it helps him in multiple ways.
Gastro tested for Celiac both with a blood test and biopsy during my colonoscopy and both came back negative. I've been eating low fat, stopped taking birth control several years ago when this started, already had cut out dairy except for fat free greek yogurt, and within the last month am trying gluten free again, just because I am trying anything at this point. I take milk thistle supplements, beet root, artichoke, probiotic, and fiber. (I use psyllium husk - been trying to avoid any artificial flavors, sweeteners, etc.)
I would really like to find a doctor that recognizes overactive gallbladder as an actual problem. Everyone I have been to thus far, has said its IBS, and its not.