A common cause of upper back and neck pain in women is lack of breast support from poorly fitting bras. This increases the load on your spinal structures and supporting muscles, with an effect that would be very similar to wearing a loaded back pack on your front.
It’s important to be professionally fitted for your bra, because your size and shape changes over time with weight loss or gain, muscle change due to training or detraining, and post-pregnancy due to breast feeding. It is probably worth being professionally fitted every two to three years in a specialist lingerie store, just to check if you’re still the same size you thought you were.
If you find an underwire too uncomfortable but you need the support, newer elastisized bra styles (ahh-bra, wonder-bra etc) can provide great support for bigger breasted women with increased comfort.
Whatever your needs, if you are having ongoing neck problems that wont respond to conservative treatment, consider whether you are giving yourself enough support, and discuss this with your physiotherapist.