Bench press will not make you lose your boobs. It can firm them up.
Losing or burning body fat can make your boobs smaller. Also your nutrition, genetics, lifestyle, can influence your chest size.
this is a great question and no matter how many times the facts get answered people still will believe this.. chicks that have their boobs shrink from exercise have that happen cause they lose body fat. you might go from a D cup to a C cup if you lose 12 pounds.