I've been excessively eating, and always sleepy, whats wrong with me ?!?

I'm 19, and I've just started eating copious amounts of food. I have had unprotected , but my question to that is if I WERE possibly pregnant, don't you have to be in like 4 months before the baby makes you hungry all the time ? I'm not gaining much weight, only to all the food I've been eating "about 3 pounds in a week or 2" and I get exhausted sometimes, and at night, I p out quicker than usual. What's wrong with me !? I want an opinion before I waste my money on a prego test. thanks ! (: