For at least the last 10 yrs, i have had months or weeks where i don't feel great. symptoms include foggy headed, bloated, muscle pain, gassy, blurry vision, etc. other times i feel great! any ideas?

Several possible dx: The long duration of symptoms rules out several things. The bloating and gas points to a GI cause (diet/malabsorption?). The fogging, muscle pain can be non specific. The blurry vision could be normal presbyopia from being over 40 yrs old . If you are worried, get a full physical.

Fitness vs Disease: Could be as simple as fitness and diet. But it could be diabetes thyroid hepatitis renal failure. Get tested by your doc or urgent care clinic! many people have poor diet and fitness. This can cause the same symptoms. Anyone with bmi of 35+, no effort towards a healthy diet or exercise is at risk for feeling lousy. Cut fatty meat by half, add hiit:high intensity interval training-only 12 min/day!

Need to check: Blood work to rule out thyroid disease and diabetes.

Hard to say: Those can be symptoms of lots of things. Have you seen your doc? Depression/anxiety can give these symptoms as well.