I'm a small 32A and 17 years old. Will my breast stay this size or it will change till I turn 20? What should I do?

Thank you for your question. Breasts can change with weight gain or loss, exercise, hormone changes, and genetics. I recommend to wait an evaluate your breast size after 21-23 years of age, and talk with a Board Certified Plastic Surgeon about your goals and plans. I hope this helps.

The rate and timing of breast development varies with each woman.  Once you've completed growing, you're most likely not going to see much change in your breast size.   However, they will change during and after pregnancy.

With the limited information available, and without the benefit of a full history and examination, I would suggest that you exercise patience and wait a few years before you make any decisions about changing breast size/shape.  At that time, if you still have concerns about breast size/shape, best to seek in-person consultation with board certified plastic surgeons who can demonstrate significant experience helping patients in your situation, achieve the types of results you are looking for. Best wishes.