2-3 weeks post-op is much too early to see much in the way of imporvement--YET. Assuming you went to an ABPS-certified plastic surgeon with excellent training, experience, and ethics, you can rest assured that something was removed in the operating room.
The problem is that there is always surgical swelling which takes several weeks to reabsorb, followed by scar induration (firmness) and lymphatic swelling (especially in the armpit area) that can take months to settle and mature maximally. Many studies confirm that healing takes an average of about 7 months, which is why we surgeons tell our patients that "final" results can take 6-12 months to be achieved (remember the bell-shaped curve centered over 7 months--some will heal a bit faster, some will take up to a year).
Sometimes the hardest job we have is to explain why "instant gratification" is usually NOT something associated with surgical recovery! Be glad you can wear a tank top; be patient and watch your diet and resumption of exercise. These two operated areas are very metabolically "active" as they heal, so any "extra" calories you eat tend to "go there" where the metabolic demands are highest. Best wishes! Dr. Tholen