Burning pain/muscle weakness

Hello. Been suffering from a weakness that progressed over years from mild to disabling. The weakness is like the muscles just don't get enough nutrients/fuel to keep working like normal muscles should- they run out of stamina very quickly now, and I have to rest for a couple hours in order to get enough energy to take me until bedtime. Things that shouldn't hurt, like typing this out, cause a muscle burning pain that is like lactic acid burn where you overwork muscles and the burning pain will start and won't let up till you stop and rest those muscles. I have several,other symptoms which I'll list:
1: brain fog

2: trouble concentrating

3: heat cold intolerance (ill,discuss this below)

4: jaw muscles get weak and cramp when trying to chew (but only at certain times when I'm really run down)

5: neck will hurt so bad I have to lay head back on couch to take pressure off the muscles- again, a burning pain

6: forearms, calf muscles most affected besides the neck- the muscles fatigue extremely quickly (like jusy brushing teeth will cause them to burn/pain)

7: extremely exhausted all the time. I sleep 9 hours at night, th3n 4-5 hours in after noon just to make it to bedtime at night again.

8: peripheral neuropathy

9: my temperature regulator is broken (I'm cold most of the time, even in summer, but will overheat all of a sudden and get very weak and sick to stomach, and shaky)

Whatever is going on causes me to become run down so badly that it takes me a few days to recover back to my usual crappy feeling self. It's like having the flue 24/7 in regards to the weakness, exhaustion, fatiguability, and muscle pain/weakness. Chores exhaust me.

I've always had my left eyelid droop when my condition worsened for whatever reason. Phots as a kid show the lid drooping.

Docs have me down as having some kind of myopathy, and chronic fatigue with possible fibromyalgia, but I have my doubts. I have none of the trigger points or tender points for those conditions. I've been trying for 25 years to find out what was going on, only to,be frustrated with all tests being in the normal range. Even the electrode in muscle tests.

I thought that my issue was a breakdown in how the muscles use the fuel from food that is supplied, and that I would run out of adequate fuel to keep the muscles going, but now I'm not so sure as again, tests always show everything working as it should. I didn't realize that MG would,cause muscle pain because of,nerve issue, and think that maybe this might explain the pain better especially where my tests usually come back normal?

I have a real,hard time with heat coupled with humidity- I get very weak and shaky, and have a hard time breathing, and just feel really off, like something is just really wrong. As a younger person I handled heat, hu idity and cold just fine- working outside in heat humidity was never a problem- then this muscle issue hit and since then just sitting around in heat and humidity is enough to make me feel really awful.

Does any of this sound like it could be MG (I know the droop eyelid and cramping jaw muscles when chewing do, but those could be related to other conditions too like fibro, if infact I do have that)

Thanks in advance, Nazareth