Pls pls answer i am having stomach heaviness...?

pls i need ur help of yours from past six mnths i am having stomach heaviness after eating .now it is getting worse n worse.i have gone to many doc but they give med. Which give temp relief and do not get cured by root.bread make it worse .i feel heaviness which last till 4 hrs (not exactly it depends on it severity)and other times my stomach is ok! Now days it is going regularly like this due to this i am not able to eat .well i m male 16 yr severly underweight problem also since 4 yrs .pls help