Obviously am not a doctor,but have very similar symptoms to you. Been admitted to hospital twice with suspected gallstones.
The ultrasound SHOULD confirm whether it is gallstones or not.
I have had two ultrasounds and a CT scan (to look for gallstones - sometimes they are v v tiny) and an endoscopy (to check whether its a stomach ulcer).
They cant find gallstones or an ulcer and my pancreas looks ok so they dont think its pancreatitis.
However, I'm being referrred back to the hospital again as I had another "attack" two weeks ago (first in about 5 months). The pain level is horrendous, v v frightening and yes, you honestly think you are going to die. It terrifies my husband when it happens.
As no gallstones have been detected, I may have to have the "more invasive" tests the hospital said they wanted to avoid on my last two stays.
I am convinced its a gallbladder problem - you can have gallbladder disease without gallstones.
I don't know how quickly you'll get your scan, but in the meantime, avoid alcohol completely and keep your fat intake low.
Hope you get it sorted out. I really sympathise because I know how dreadful the pain is.