Why do my old bras still seem to fit two weeks after my breast reduction? Going from 34F/G to 34C. (photos)

Two weeks is very early in the recovery period and it is normal to have substantial swelling at this time. You can anticipate a significant volume reduction over the next few weeks. If you are curious as to your future bra size, your surgeon should have records of the weight of the tissue removed and may be able help you to roughly extrapolate this from the data. 

Thank you for your pictures and questions. The bottom line is that yes, it is too early to be concerned. At two weeks, you still have a significant amount of bruising and swelling and it will take at least three months for this to fully resolve. Try to be patient and keep in touch with your plastic surgeon. Best of luck!

Thank you for your question and the photos.
At two weeks after breast reduction you will still have quite a bit of swelling and it's too early to be concerned. Your early results look quite nice and rather than getting overly concerned over wearing a C cup but rather having matching body proportions which it appears you are approaching once the swelling resolves.  
Best Dr. L