When I was at a private Catholic school, I was a barrel.(Also, as someone who's basically a square block, I feel your pain on those shirts - I had a seventeen-inch neck in high school, and had to wear dress shirts since I went to a private Catholic school. Anything that fits across my shoulders is either swimming on me everywhere else or way too long.)
But I decided to take care of the stuff that was genuinely my fault when I went to college. I changed my eating & drinking patterns and RADICALLY increased my physical activity level, finishing my first semester 50lbs down. Add in a growth spurt, and I graduated at 5’7”, 193lbs…and scary.