Pull your jeans up!
And tidy that room!
lol
nah just kidding m8, a good platform to build on is that. I have the exact same body type as yourself and was exactly the same as you at your age except I am a little taller.
After a lot of effort and a lot of food I have now gained to almost 14 stone and am still growing.
Keep at it, and don't worry about how you look now, think of how your going to look and focus on it
Cheers