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.

Back pain may or may not be related to the large breasts, but large breasts can certainly put strain on the back.  A breast reduction may or may not improve your 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.

The normal range of breast sizes is A - B - C cup size. In effect the female chest seems to be built to accommodate breasts in that size (and attendant weight). D cup and larger size breasts are outside the normal range and can cause problems with or without the support of a bra. Like most things it's usually better tolerated when young, but strain on the back, spine, and neck generally eventually cause problems. Sometimes volume can be more fatty than glandular. Fat is relatively light -- floats on water -- glandular breast tissue is heavy. There is some debate on how much beast implant volume/weight adds to this problem. Another factor is the contribution of sagging of the breast off the base. Another is activity level. Women in sports usually don't want breasts larger than an average B cup.