Check for Mold, Gasses - Carbon Monoxide, Radon, etc, Lead. Work down your diet - try process of elimination diet to detect any food allergies. You mentioned food sensitivities - often where there is one, there are many. When eliminating foods, look at ingredients: MSG, refined sugar, white flour, wheat, yeast, Gluten and other preservatives. Eat whole, live foods as much as possible, avoid fast food, processed, fried, boxed, canned, etc. Eat organic meats, steer clear of milk and soy, try lots of fresh fruits and veggies. If not fresh then frozen veggies is next best to canned.

Eliminate chemicals from your life: fluoride in toothpaste and mouthwash (and water if you live in a fluoridated area) can have long term and cumulative health effects, sodium lauryl and laureth sulfate in shampoos and many other products are industrial strength detergents and degreasers. Keep in mind that all the chemicals you use every day (Aluminum in deoderants) are being soaked up by your skin, breathed into your lungs and absorbed into your body every day. These chemicals build up storing themselves in your vital organs, bones, fatty tissues, muscles, etc.

I have to honestly say, it sounds to me like something is poisoning you.

Hope any of this advice is helpful.