What Causes Severe Fatigue And Nausea Along With Excessive Sleepiness?

I usually love sweets, but 10 days ago I became extremely weak and nauseous and slept for a lot of the next 36 hrs. I ate toast and crackers for the next couple days. For the last week, the only thing that sounds appealing to my appetite is salty organic pita chips and baked potatoes with a little butter and a lot of salt. At first I wasn t concerned and figured my body knows best and I needed easy to digest foods. Now, especially with me being a health nut, but still a sweet tooth junkie, I am concerned that I do not desire any sweets, protein or the 120 oz of water that I normally consume everyday. I sincerely have only eaten baked potatoes and chips for 7 days in a row and made myself drink about 90 oz of water and take a multivitamin. What do you think? Thanks so much!