If you lose weight, there's a chance you'll stall at A cup and your band size will probably decrease. That's what happened with me, went from 38B to 32B, that's a huge difference in size, its not just the breasts that shrunks, the back muscles and pectoral shrunk too. It depends how much muscles you had initially. Since you've got a 33 bust, I'm guessing you didn't have much upper body muscles initially. Me I had a 40 bust with no breast tissue initially, now with breasts I'm around 35.5.
Audrey, you should concentrate more on building muscle mass instead of doing aerobics. If you muscle mass is low and you don't sustain it, aerobic doesn't work very well, it will just shrink your muscles and fat at the same time making it harder and harder to lose fat. That's the most common problem with women doing exercises. Then they complain they don't lose weight!
So, do muscle building exercise for the buttocks, and core muscles and the upper leg muscles.
Don't do little piddly weight, that won't build muscles. Find a trainer at the gym to devellop a serious programme for those parts.
As an extra, this makes you look shapely :-). Look at figure skaters, they've got a LOT of lower body muscles and they look GREAT.