My breasts are a size 42DD. Why does my back always hurt?

If your breasts are large and pendulous, they will pull you forward and weigh you down.  This can cause back pain.

Back pain, neck pain, shoulder grooving, rashes between and under the breasts, and numbness of the hands are some of the most common symptoms of breast enlargement. The symptoms are caused by the excessive weight of the breast tissue and the impact it has on your posture.  A breast reduction is an effective procedure in addressing these symptoms.

I am sorry to hear about the pain you are experiencing but you will be best off seeking consultation with your primary care physician;  working together, you will be able to make a diagnosis of the cause of your back pain. Sometimes, breast hypertrophy may be the cause of upper back, neck, shoulder discomfort; if this is the case, then breast reduction surgery may be indicated. This operation tends to be one of the most patient pleasing operations performed. You may find the attached link, dedicated to breast reduction surgery concerns, helpful to you as you learn more. Best wishes.