what is the reason of loosing weight?

Sir, i masturbate almost every day since 8 years i became very thin and feel weak,, and i am not able to get out of this habit, is it really that harmful? another thing is that i feel hunger but i can't eat more than 1 or 2 slices of bread. my age is 23 years and my weight is only 43 kg. Please suggest a way.