I had many of the same symptoms and have been diagnosed with CFS. After endless research, I stopped drinking diet soda with Aspartame, stop eating Sugar and flour. That pretty much cleared up the joint pain, dizziness, loss of muscular control, fogginess, slurred speech, etc.
I'm not saying that the Aspartame caused it but I know when I was drinking regular pepsi and getting fat, I didn't have any problems. Now, I can only drink 1/2 diet soda before I start getting a headache. Too bad they don't make diet vanilla pepsi with splenda.
Diet rite is a good soda to drink if you need to have soda.