Bumping this thread! I know it's ~6 months old but no need to start another topic about this.
Anyway, I wanted to inform you all of a store my friend recommended to me called Uniqlo. They're a pretty new company, they just opened up a store near me last month and I went there for the first time today. I really liked it a lot, cool clothes, good prices, and the best part, they have size XS for men! I like my new shirt so much I'm gonna post a pic of it so you can all see how awesome its design is/how well it fits

Ok ok that's enough, I swear I'm not tryna advertise for them and don't work for them lol.
My other suggestions would be, American Eagle, 100% agree with everyone who mentioned them. They are my favorite store and probably make up about 70% of my wardrobe. Express, they also have XS shirts and fit really well. I like Abercrombie too but only for certain things... their button up shirts size S fit me great. But some of their other stuff has a weird fit to it. Aaaaannnnd yep, that's just about the only places I shop. Sometimes I try to branch out but am continuously disappointed with how huge most clothes look on me. So f it, I'll just stick to my few trusted stores, why fix it if it's not broken?