Should I get a Reduction of just a Lift?

I am 17 years old, 5'6 148lbs, size 7/8, and I wear a 36DD, almost a DDD. I saw a plastic surgeon years ago about getting them reduced, and he said that he's seen other people with bigger than mine, and that I didn't need it. I have back pain occasionally, and find it difficult to participate in sports. I even have difficulty sleeping comfortably. My also hang very low, and I have yet to have kids. I do want to have kids eventually, but that might not be until my 30s, and I don't want to suffer for years with this problem. I really want a reduction, but it seems like you have to be over 30 and have DDD or above, and overweight to get a reduction. I'm comfortable with my bra size, I just wish my had shape to them, and didn't sag and get in the way. I'd like to be a full C or D though. I would really appreciate it if some people could give me some helpful answers. Thank you!