I Am Having Some Strange Symptoms For Two Weeks Now.

I am having some strange symptoms for two weeks now. I have bouts of bloating, building nausea, and stomach cramping capped off by a series of stronger dry heaves than I have ever experienced before lasting from a minute or two to five minutes, accompanied by a cold sweat. Then, I feel better for a day or so (except I am exhausted) before a repeat. It doesn’t seem to be associated with eating necessarily, and I rarely vomit. I have been tested for gallstones (negative) and had a HIDA scan, which was normal. I have been recommended to a gastroenterologist but it is difficult to get an appointment. What are the possible causes of this?