I've always been against changing your body in any way (ie breast enlargement, lypo suction, etc), but I've always agreed that breast reduction is a good idea if it's a medical issue. I say look into it since it's hurting your back and shoulders. However, I hope you realize that you're beautiful just the way you are and don't need to change.
*Randomness*I also wanted to say that I'm now proud to have smaller breasts. I used to want breast enlargement, but now I'm like "What's the point?" We do have some advantages. Besides, they'll never sag!