Why do I wake up tired and weak on a daily basis?

On almost a daily basis, I wake up feeling very drained regardless of how much sleep I get. My body is weak and I need to get breakfast ASAP. I have had episodes in the past where I became so light-headed that I "fainted"; by this I mean, I dropped to the floor and blacked out but was still fully conscious. It lasted about 30 seconds and happened to me twice -- hasn't happened for over a year but I still wake up a bit lightheaded. I am a vegetarian so I am wondering if the cause could be iron deficiency (I do eat fish on occasion so I guess you could call me a "pescaterian"). I try to eat healthy and take a multi-vitamin to replenish anything I might be lacking in my diet but maybe I need to be taking iron on its own? Or maybe it is something more serious. Both my grandfather and grandmother had diabetes so that has me really freaked out although, I don't see why I would have it this young, I'm only 23. Any insight would be really helpful. I will eventually visit the doctor for this but it costs me $120 just to walk into his office so I can't go immediately. :)