I'm 15, and have 32F breasts. Should I get a Breast Reduction?

Breast reduction is a great surgical procedure for patients that are having issues with back and neck pain, shoulder grooving, psychological distress due to their large breasts, etc. This seems to be happening to you even though you are only 15. I don't think that this is too early to consider the procedure, but there are things to consider. You need to have a complete understanding of the surgery, its risks, and the possibility that you might have juvenile virginal hypertrophy which is a condition that might require another breast reduction later if the tissue continues to grow. You will need the support of your parents as well. But the surgery could certainly benefit you and would be something to discuss with a board certified plastic surgeon in your local area. 

I'm sorry to hear about the physical and 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.
In my practice, timing of breast reduction surgery is determined on a case-by-case basis. It is not too early to do your homework and 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.
As you learn about breast reduction surgery, make sure you read about the potential risk/complications associated with the procedure. You may find the attached link helpful in this regard.  For example, unsatisfactory scarring is  one of the potential complications. Make sure you also understand that further surgery may be necessary in the future (for example if the breasts were to grow in size again).
On the other hand, breast reduction surgery is one of the most patient pleasing operations we perform and I think that for the right teenager (enough symptoms) it may be an excellent option (regardless of the age).

Sometimes breast  reduction surgery is covered through health insurance. The best way to obtain insurance coverage for breast reduction surgery involves some “hoops” to jump through. The more documentation you have (for example, from your primary care doctor, physical therapist, chiropractor etc.) the better when it comes to obtaining insurance “authorization” for the procedure.
This documentation and letter/pictures from your plastic surgeon will help you obtain authorization.
 When the time is right,  seek consultation with well-trained/experienced board-certified plastic surgeons.
I hope this, and the attached link, helps.

With the amount of symptoms that you describe many plastic surgeons will consider you for a breast reduction with your parent's permission.   Of course, this requires an in person consultation so that you can be examined and interviewed by the surgeon.  Make sure your parent or legal guardian are with you during the consultation. Best of luck.