About weight, but confusing ish..

Okay so it’s quite a long story but I will try to shorten it.. so I weigh 74 pounds and I’m 17 so I HAVE to gain weight…like I eat and everything, I don’t have an eating disorder trust me.. I’m just small. So I’m going to up my calorie intake and start eating more and drinking pediasure and protein drinks to gain muscle/weight…

I’m pretty skelator obviously, except I really do have quite a bit of lower fat on my stomach… but I know I need to gain weight.. but I’m afraid if I start eating more and using protein shakes (which was recommended) then it will all just go to my stomach, and the only thing that will get fat is my stomach… is this true or will it fill out my entire body? is there anything I can do to prevent it from just going to the stomach? I want to gain weight I just don’t want my stomach to get huge..

any advise? please help…