Can I get reduction from 28E to 28C?

I'm sorry to hear about the physical and (probable) psychosocial problems your disproportionately large breasts are causing you. 
It is probable that you are dealing with juvenile breast hypertrophy along with the physical and psychosocial consequences of this diagnosis. In other words, the breasts are too large for your frame causing  both physical and psychological distress.
Based on your description you may be an excellent candidate for breast reduction surgery. It is one of the most patient pleasing operations we perform.
I would suggest that you learn as much as possible  about  breast reduction surgery and the potential risks and complications associated with  the procedure.  Hopefully you have the support of your parents as you do your homework.
Unsatisfactory scarring is  one of the potential complications. Make sure you also understands that further surgery may be necessary in the future (for example if the breasts were to grow in size again).
It is possible to reduce the breasts size very significantly.  The concern with the amount of tissue removed is related to blood flow to the remaining tissue;  if too much tissue is removed in one operation the blood flow to the remaining tissue (including nipple/areola)  may be compromised.   Part of the tissue that is left in place is called the “pedicle"; this segment of tissue is responsible for delivering the blood supply to the nipple/areola tissue. If the pedicle is made too small (in the effort to reduce the breasts as much as possible)  then patient will likely have problems with tissue survival.  
The other concern with overly aggressive breast reduction surgery is patient dissatisfaction  afterwards.  It is not unusual for patients who have lived with very large breasts to want to have as much as possible removed. Care must be taken to be judicious in this removal to avoid an outcome where the breasts  are too small in relation (proportionately) to the patient's other body parts.  Again, it is not uncommon, for patients'  breasts to become smaller ( after the breast reduction procedure) with time and/or weight loss-  breast augmentation may become necessary to achieve the patient size goals.
I hope this, and the attached link, helps.

At 16 you may or may not be a candidate for breast reduction.  The procedure at this age is a little controversial as the breasts may still be developing.  The risk is that even with a reduction if you are still growing, the breasts will continue to enlarge and you may require additional surgery for reduction.  I tend to wait until women are fully developed with a stable breast size before considering breast reduction surgery.  The best way to determine if you are a candidate is to schedule a consultation with a board certified plastic surgeon with experience performing breast reduction surgery.  They will be able to assess you, determine your candidacy, and explain the operation  and it's associated risks and benefits to you and your family.