Fainting, 3 months pregnant?

I have to eat even when Im not hungry just to feel normal. Everyday I as soon as I wake up, I am shakey, headache and I have to eat SO MUCH than I normally do. Last week I scared myself because I ate a salad for lunch, and about an hour after that everyone sounded far away and i fainted while I was walking to the couch. Im 3 months pregnant, what should I do? Can the doctor help?