I Have Severe Pain Between My Shoulders. Had An Ultrasound

I have severe pain between my shoulders. Had an ultrasound of my gall bladder, liver and pancreas as well as a nuclear stress test and nothing was found. Are there any other tests that I should have. My doctor told me to take Tylenol extra strength and nitroglycerin for it. I have taken the Tylenol and it helps but the pain is back in a few hours. I also have acid reflux and diverticulitis but manage those with diet.
Thank you!