Food doesn't say in stomach,no pain

I have this weird problem,no matter what i eat,no matter the quantity,if its fried chicken or a just a toast,nothing stays in my stomach,within hours i have diarhea,i didn't paid attention to it,and at the begining it was "fun" starting to loose weight,but now i can see that i am getting thinner and thinner,and thats scary,i don't feel tired,or dizzy or anything,i feel normal,i am guessing i am guetting the nutritions i need before the food goes out,or maybe i have resources to burn from my body,and if i get slim enough i will have this symptoms,now i am curious what is the problem i am having,could it be an infection or a bacteria?Thanks