Gladmorning - are you sniffing anything icky ???? meaning do you have one of those flyspray cans that squirt spray every 30 minutes?, or one of those car air fresheners?, or do you wear perfumed hairspray, underarm etc...... are you working in an air conditioned room?, do you work in a job that requires alot of computer screen work or fine print small reading?, have you had your eyes tested recently ?
just a few of my initial thoughts.
I agree that you may be lacking adequate minerals & sodium. And drinking over a gallon of water a day may be exacerbating the problem.
Absolutely Stop drinking all that water, you're flushing out all the minerals and water-soluable vitamins. Next stop eating any nightshades, which for me includes white potatoes, tomatoes, all peppers and pepper-derived spices, and eggplant. If you're in the first 2-3 weeks you might still have 'carb flu'. If so, it will go away soon, just gritt you teeth and keep at it.