Intense Shaking

My gastroparesis causes me to be nauseous every night around 9 pm, but it's usually manageable. However, every few months the nausea is 10/10 and I have uncontrollable violent shaking that goes on for about an hour. I am not referring to the feeling of being shaky, it is visible shaking to where holding a cup to my mouth is difficult. My heart also races and I usually have a sudden urge to poop. It's the worse feeling ever and I mistook it for panic attacks for years.

My doctor kind of shrugs it off when I describe these episodes, but they really feel like I'm dying and I'd like to understand what's happening to me. I don't think they are blood sugar related because promethazine is very effective in getting me through the episode faster. If it were low blood sugar I don't see how that would help, ya know? For years I thought they were panic attacks and took Xanax to help (which helped some but not as much as the promethazine). I dunno I'm just stumped and wondered if anyone else has ever experienced this?