Yes it really does sound postural - you could investigate a posture support brace although you'v said you have good posture so it may not be. ensure regular breaks from the computer where you walk for a bit.
One of the best things you could possibly do is start swimming - freestyle/frontcrawl and backstroke will help to strengthen the muscles around the thoracic spine.
Holding a sustained posture will make you sore and the longer that is held the more the tissue involved becomes intolerant, reducing the time it takes for the pain to come on and the stress involved to bring it in. If you have periods during the day when you have no pain then you have every ability to be pain free all day. We just have to learn how to make that painfree posture the same as your work posture.
With seeing that many professionals I suspect that you would have had this advice before... Try swimming and scap stabilising exercises if you haven't already. good luck and let us know what your doing if it starts getting better.