19 weeks post breast augmentation. Capsular contracture vs muscle tightness? (photo)

Sorry to hear about your asymmetry.   It is difficult to make a diagnosis just by looking at your picture.  Though rare at 19 weeks, it is possible that you have a capsular contracture.  Your PS should evaluate you in person and make recommendations such as massaging techniques, Singulair, Vitamin E,  possible ultrasound or Erchonia Laser treatments, etc.  

You are still fairly early in your healing process, and your higher implant appears to have not completely dropped.  Sometimes it does take 6 months for the breasts to completely settle. Please let your surgeon examine you. External ultrasound treatments and Singulair could be helpful.