Feeling so weak and tired lately, no appetite, craving bloody meat?

I know I should go see a doctor, but would like to know what could be causing this. I've been feeling weak and very tired lately, i could probably sleep all day long if i didnt have to go to work. Even at work i kneeled down to get something and i was so tired i wanted to fall asleep in that position it was hard to get up. I exercise each morning 5 times a week, but am completely drained after but not hungry at all i just wnat to sleep. I do try to eat but when i do eat it makes my stomach hurt like crampy and diareah and i crave bloody meat.