Re: tingling/numb spot with back pain???
I, too, had a stabbing, tingling, numb spot in the middle of my back, just to the right of my spine. My chiropractor said it was a pinched nerve due to a curvature of the spine (as might be caused by large breasts, in your case). It was agrivated by the use of the computer mouse. I give the computer use most of the credit for my pain.
Then I saw my Massage Therapist who gave me a really good treatment that loosened up the muscles in my back, shoulders, and across the upper chest. This has relieved the sharp pain in my back, and allowed me to stand straighter than I have in years. I must be 2" taller this week! Check your area for a good Massage Therapist and see if that doesn't help. It certainly won't hurt. Look in the Yellow Pages under Massage Therapy, or under Schools, Massage Therapy for a referral (or your beauty salon or chiropractor may have one on staff).
Actually, I am a Massage Therapist myself, but also had trouble finding someone to work on me. I am so grateful for finding one at last.
Good luck, and let me know if there is any way I can be of help.