sounds so familar...I was in the same situation when I was 16...and wanted to gain weight.
Wish I could turn back the clock....I did start to gain weight...and more weight.
Before you know it you have gone past your ideal weight and then trying too loose it becomes a mare.
Be happy with your lot....because on this game...the weight gain will follow...I've yet to meet a T1 who is happy with their weight...and once its on...its hard..real hard to get it off..exercise, risk of hypo, etc.