Definitely sounds like Fibromyalgia . See if you can find a good rheumatologist.

Nausea can be caused be liver malfunctions such as gallstones or pancreas problems.

I would fet with a gastroenterologist. I have gastropareisis and nausea, and inability to eat with fatigue but with constipation. Get checked out!

Peppermint tea for nausea, or peppermint.

Nausea sucks. I have to take promethazine regularly. Sorry you feel so bad, BUT you don't mention ALL OVER body pain! So I vote no on fibromyalgia. But what do I know? So research FMS to see if your symptoms match better. Do you have the minimum 11 tender points?

Unexplained body pain is the #1 symptom of fibromyalgia. We're talking all over your body, every inch, every second of every day. I hurt so much that I dread going to bed because it takes too long to fall asleep and without constant distraction of TV, all I can do is lay there and count the pains. I'm lucky to get 4 hours of sleep because I wake up constantly thanks to some strong pain. And I'll try anything I can think of to help ease it some. Usually I also face nausea because of the pain levels are so high. So unless you add serious body pain to the top of your list, I'd say, keep searching for an explanation.

Have you considered migraine disease? There are many different types of migraines. If it happens only 4 times a year, I'd wonder about migraines because migraines are not just about a headache. They are a neurological event in the brain, so symptoms can be very different and weakness could definitely fit in with migraines. There are abdominal migraines that cause severe sudden nausea, but without severe head pain. I don't know if an ache at the back of your head would rule that one out or not. There are other migraines that can literally freeze your body, unable to move for hours. Others that temporarily blind you. Some give you aphasia, unable to speak. I have Todd's Syndrome which distorts my visual perception and my world turns into topsy turvy like Alice experienced in Wonderland, thus the name Alice in Wonderland Syndrome (AIWS). There are SOOOOOO many different weird types of migraines, so you definitely need to rule that out by a neurologist.

A rheumatologist might be a very good source too because they run different tests than a regular GP. So although you're frustrated, don't stop searching. I've been sick most of my life and only now at 69 am I finding some answers. My AIWS wasn't diagnosed until 2013 in spite of having 5 other neurologists. So don't give up!

My FMS was diagnosed first by a physical therapist just out of school in 1978, but it took another 15 years before a doctor recognized it and I got my official FMS diagnosis. So hang in there!