The only thing I can think of is the jacket is probably too loose. Your jacket should be fitted, if you can grab the chest of the jacket and pull it outward at all then its too loose.
Not zipping your jacket up all the way only makes the problem worse so make sure you're zipped up all the way if its ballooning on you
Not zipping your jacket up all the way only makes the problem worse so make sure you're zipped up all the way if its ballooning on you