Tight tops look great on me until?

I'm 18, 5"4, my measurements are 41-29-41, and I weigh 159lbs. Tube tops, singlets, etc all look great on me in the morning, before I've had anything to eat, but as soon as I even have half a gl of water, I develop a food baby that looks so bad I have to change into something else. It's not really bloating, because it happens after I eat or drink anything, and it wobbles like crazy. Why?