Dealing with nausea, dizziness, muscle weakness, twitching, numbness, and weight loss...

Regarding those muscle issues... honestly, I suspect it’s a simple case of sheer inactivity. Are you all actually getting any exercise? Look, I'm significantly younger than most of you, but I haven't been particularly active lately—blame the college lifestyle—and after attempting just ten minutes of light movement, I was literally shaking from weakness for hours afterward. It was a struggle just to make it back home. My conclusion? It matches exactly what my physical therapist told me: muscles lose their strength when they aren't being used. If you sit around like a houseplant, you're going to feel it. You really ought to see a specialist to get a proper evaluation and a tailored therapy plan... I’ve started some gentle physical therapy exercises myself, which have been a lifesaver for my back and neck (I deal with scoliosis), but you need to find a form of recreation that actually suits you. Don't force anything that feels unnatural.
2. Iron levels—how are yours looking? I get those same bouts of sudden weakness you're describing. Whenever it hits, I make sure to drink water with a bit of sugar, or maybe a Gatorade or some lemonade... it's that terrifying sensation where everything goes black for a second. I've been dealing with iron deficiency since my teenage years.
3. Blood pressure? What are your readings? It could be the same thing—dizziness, lightheadedness, seeing spots, or just general exhaustion caused by low blood pressure.
4. Stress—you really have to try to shift your lifestyle, even if only incrementally. Carve out at least thirty minutes a day just for yourself. Instead of driving to work or taking the bus, try walking part of the way; instead of collapsing in front of the TV the moment you get home, go for a short walk.
5. Multivitamins—give them a shot for at least a month; you should start feeling a difference.
In my view, this isn't necessarily anxiety or hypochondria—or anything quite that dire... at least, not yet. It sounds more like burnout. You need to change certain habits, starting with physical activity. Every Sunday, head out to a local state park or a hiking trail... it will be difficult at first, certainly, but if you stay consistent, you'll see the results sooner than you think.

Have you guys looked into finding a vestibular rehab center yet? I can't even remember the exact name they use.

Thanks everyone for all the advice and for looking out for us! Sorry we haven't checked this thread or anything else in a bit—we just got caught up in a whirlwind of doctor appointments and testing. Long story short, it looks like it was probably a perfect storm of several things hitting at once: stress triggers and diet. (It’s still an issue, but way more manageable now). We found out there's a severe food allergy, though interestingly, he never actually dealt with hives or swelling. The tests also pointed toward some mild pancreatitis and some issues with his cervical and lumbar spine. As for the H. pylori, he managed to clear that right up using okra, which worked like a charm, along with high doses of probiotics and natural digestive enzymes like papaya and pineapple.
The insulin test results weren't great, so we're still waiting on the follow-up for that. Lyme disease has been ruled out, though. Honestly, ever since he cut out the specific foods causing the allergy, almost everything has cleared up—he even stopped losing weight. He still gets hit with the occasional flare-up when he's under extreme stress, but it's nothing compared to how bad it used to be. I'll keep you guys posted if anything else pops up (we've still got some bloodwork pending for reproductive and adrenal hormones). Anyway, thanks again for everything.

Since I’ve been getting a few DMs about this—and honestly, I’m rarely hanging out on the forums anyway—here’s the final breakdown of everything that’s been going on: a lot of stress, insulin resistance that was basically turning into type 2 diabetes, food allergies, a H. pylori infection, and some minor issues with my neck.
He tackled the H. pylori with okra, and he’s managing the blood sugar and allergies through his diet. He’s still working on his neck, too; he was already active before, but those TRX workouts probably actually made things worse, so now he’s sticking to lighter isometric stuff. As for the stress, switching jobs pretty much solved that.