Very stiff/tight upper back -suggestions please

Hey FB family,

How are you all doing?

I reach out to you hoping for some stretching (or other) suggestions: despite proper warm and cool down stretches my upper back stays very stiff. For example stretches like shell stretch or chest opener (in warm ups usually) help me the most or toe touches but with rounded back. Is there anything else I can do to help relax and stretch those muscles. Must also mention I work sitting (with a supporting back cushion) at the desk most often but move from time to time.

Thank you very much!