give up

I want to gain weight.I do think this before that how to gain to touch my ideal weight because my weight now is still underweight with the calculation of body mass index.I think i'm eating well-balanced diet.More vegetables than meat,less oil and sugar.But couldn't touch the normal weight.If i really reach the ideal weight,i dare not to imagine how will i looks because around 13 till 14 kilograms i need to gain to reach the ideal weight.Feel crazy and give up on gaining weight.