Can I wear an undershirt for sports and stuff?

Hey, I couldn't help but wonder whether or not somebody my build can wear an undershirt for like athletics and everything... I just don't wanna look really weird in it, i mean don't wanna be a huge guy trying to be thin... but anyways I'm about 5'7, about 126 pounds, and i'm no buff stud i don't have any kind of six pack or 4 pack or anything but not incredibly big either, i mean when i ask people they all tell me i'm really not fat, would you say that I could pull it off??