It seems that you have some pinched nerves in your mid-back and they would have to be reset soonest. This type of pain is not connected to carpal tunnel problem.
As to the fitting of a bra, most places do not have the proper person to measure for a bra. Even if they have had some kind of a course, look a them and they are badly fitted themselves.
If you want to know what to wear for a bra, have someone measure you as follow: " 1. measure below the breasts and with the bra on; 2. measure on the breasts with the bra on; 3. measure above the breasts with the bra on; 4. measure below the breasts without the bra; 5. measure on the breasts without the bra; 6. measure above the breasts without the bra; 7. standing up, measure from nipple to nipple; 8. bend down and get measured from nipple to nipple. Than forward these measurements. I will let you know what is your size bra you should wear and no underwire type bras. Not even the push-up type bras.
By wearing the proper type and size bras, you will feel much better and all that will be left, is to have those nerves reset once and for all. See a special massage therapist and tell him/her to work on your mid-back to reset these nerves.
Meanwhile, use and electric heating pad all night for about 5 to 7 nights. If no electric heating pad, use a hot water bottle and do the same. For a start, take Ibuprophen pill 2 x 400 mg for the pain every 12 hours. These are over the counter type pills.