When will my boobs stop shrinking?

so pretty much ive been dieting and excersizing fairly deligently since Oct. and have lost more or less 18 lbs- which with x-mas isnt fearful... anyway my tummy is getting firmer so are alot of other parts, but my boobs are straight up shrinking!- ive gone from a DD to almost a C- my D bras are fitting loose- and its just the cup not really the tie.. anyway i just needed to know if anyone else has simular situations and can maintain me optimistic- thanks!! The method I see it is, would you rather own a flatter and firmer tummy and slightly smaller boobs, C is considered by most as a perfect size, or huge boobs and those 18 pounds rear on your body?
All boobs are is fat! So if you lose mass your going to lose your boobs to.