My advice: Don't try to solve every piece of the puzzle all at once, you will never know where to start, and if you end up stumbling over something good, you may not give it enough time and you may start your search over.
My advice would be to
1: Destress with meditation 30 minutes a day
2: Exercise every day (most here are not healthy enough to even exercise, if you can exercise you have something going for you!)
3: Take your vitamins. I HIGHLY recommend fish oil 2 grams combined epa/dha with about 1200mg epa and 800mg dha. Fish oil is a blood thinner and helps the heart. Fish oil will help blood circulation to your brain.
Then, I highly recommend a multivitamin and 5000 iu vitamin d3 per day.
Eat healthy, vegetables like broccoli, fruit, protein from eggs, chicken, red meat. Don't touch candy bars, and eat foods like pizza sparingly.
Don't starve yourself with anorexia, that is actually one of the easiest ways to dysregulate your immune system and get an infection. Eat well, if you are 175 you need about 2500-3000 calories if you are exercising every day.
Really give the meditation, diet + exercise a shot. I would not worry about heavy metals and such until you do the routine things first. Give it 2-3 months or so, and stop researching about stuff and just relax and enjoy life as much as you can.