When I was your age I had your bra size and I was 130 pounds -size 4/6 bottoms at 5'10". I have exercised as a weight lifter since I was 16. My breasts never reduced. I've been large chested since 5th grade...even wearing my mom's size C bra. The size of my bra has fluctuated with pregnancy and weight changes but not hugely. Sorry for the bad news. The good news is weight lifting will do a couple things - one, it lifts them up and two, it increases the strength of your shoulders, neck and upper back which helps in carting them around. You will see an increase in your back size. So, my current bra size is a 34FF (still lifting at 42). When you're a little older, after you've had children and finished breast feeding, reevaluate your situation and turn to insurance for a reduction. I am currently in the process of meeting with plastic surgeons. Doing this beforehand can ruin your breastfeeding and they may increase again or completely deflate. You truly can never tell what your body with do with pregnancy.
Good luck and take care. And remember your body is beautiful no matter the size! It's all in the attitude. :)