weight problem

Hi Ive been having a problem with gaining weight im 20years old, 5'7", and 125lbs.  I cant gain weight.  I eat so much food a day.  Some people have said that I have a fast metabolism but this has been ongoing for 3 years now.  Ill be at 125lbs the drop to 120lbs then go back up.  Ive even tryied taking weight gainer from the local GNC but had to stop after a week do to stomch pains.  I have know idea what is wrong with me. Pleas help asap.

[AndiJ78]

Have you talked to your doctor? In some cases there can be a medical reason behind it, but more than likely it could just be a matter of metabolism. My husband had the exact same issue, tried all sorts of weight gainers, protein and carb combonation diets, etc. Now that he is almost thirty, his metabolism has slowed a bit and he is finally gaining weight.

Andi