Congratulations on your weight loss!
How does the dress fit through your waist?
If it's just tight in the chest, the best thing to do is a minimizing bra. If it is a little too tight else where, try a shaper.
Also change up your excerise routine. Instead of the treadmill, try the elipical machine. Or if your walking, try walking, then running for a minute, then walking again, then running. Things like that help.