How do i gain back my appetite?

I lost my appetite for this few week,lost alot weight.there is something cheerful and oso something dat making me sad.the cheerful stuff is my body weight decrease for 4kg and its a success,ya,for sure my body are better now..but hopefully my parent wont's saw this post,becoz i feel dat my peptic alcher is attacking me again.coz of the vommited i experience tis few day.those excercise and vommit really making my body to be fit.hopefully can be a muscular man xD..How do i gain back my appetite?only ate 4 meal for 3 day.How?