Does Anyone Else Experience Feeling Fatigued and Faint All The Time?

I've been feeling this way for about 6 months. It seems to be getting worse. I'm just so tired all the time. It's like I'm drained of energy. I could sleep about 18 hours a day if one let me. I also experience feeling faint quite often too. I feel like I'm about to lose consciousness but never do. I usually have trouble walking and feel not exactly "right in the head" if you get what I mean. I went to my OBGYN today to see if they could help. Tomorrow I'm supposed to have labs done. My doctor told me she doesn't think it's my thyroid or anything to do with sugar. Not iron either. Glucose and CBC is always fine. I was thinking possibly Vitamin D? There's two others she's wanting checked, but I can't recall the names of these tests. She's suggesting I go back to see my neurologist. This is actually sounding a lot more complicated than I thought it would be. While I have been in school, I've often had to go see the nurse because I look as pale as a ghost and feel like I'm going to drop on the floor. I also experience hot flashes with this as well and nausea. She's told me she doesn't think it has to do with my intake of liquids but told me to keep a water bottle on me at all times to sip on. Anyone else ever had this or something similar?