i really really understand how you feel.
have you try weight gain appeton, or gnc or stuff?
but this will need you to work out a bit.

but my friend had try one ubat ginseng. pil gemok ginseng. sounds funny isn it? but it really works.
she gain her appetite and within a week she gain about 5kg.

haha she was very skinny back then. Her goal is to get an ideal bmi. 5kg didnt make her look like cow fat. she's looking great now.