Okay so in the past year I gained about 40 pounds, mostly muscle, and I'm now 166 pounds at 5 feet 8 inches. But for some reason, I still look really small and can still wear small sized t-shirts. I am 18 years old and I was wondering if there was anything I could do about my small body frame. Should I gain more weight? Do certain exercises/breathing exercises? Do you think it'll grow larger, since I kinda hit puberty late anyways? Or is it just genetics that my rib muscles are sorta small? Thanks