I have a perfectly nice heavy chambray shirt with a strange problem. When I put it on, it seems to fit and feel fine--the shoulders are where they belong. But in a few minutes, the collar is trying to escape down my back, the button is choking me, and the shirt looks . . . odd. There is something off about me, or it, or we are just bad together.

I'm hard to fit in a button up shirt, being petite and busty, and there is often a button gap problem, or just something that makes this a not very flattering look on me. This one came from American Eagle and, probably because of nicely placed pockets, isn't unflattering. But the fit problem! Any insights, so I can avoid a repeat of this problem?