Hot fermentation and posture corrections must. Avoid toward bending and stretching exercise of neck full spine extension

First you need to understand the triggers that are creating problems for you Check out this video how prolonged sitting is the culprit and how you can overcome the issue. Second video is for exercises that you should do regularly not only when you have pain. https://youtu.be/Q5pGUwvtKv4

It may be because of poor posture..

As per your complaint, it's due to prolonged sitting in front of system, so avoid it , give gap every half n hr. Maintain sitting ergonomics  its there on YouTube. No exercise when pain is present let the pain subside then you can visit physio clinic for strengthening n stretching your back region. I won't suggest you to visit clinic at this pandemic situation.

Now a days due to work from home many gets this upper back pain below neck as you mentioned. Try to be at correct posture while at work. Apply hot application.  Reach your near by Physiotherapist and take manual therapy. Once your pain gets reduced you can start to do strengthening exercise.

Applying hot water fermentation will be helpfull in reducing pain, maintain proper posture while on work, if not the condition worsens. Visit nearest physical therapy centre and take manual  therapy for trapezius muscles, the pain will reduce within no time and also later with exercises you can stregthen upper back shoulder and neck muscles.

Firstly , It is normal for a IT Professional to develop upper back pain due to overuse . One probable cause could be that your hands constantly are on the keyboard. When you type your entire shoulder muscles are also involved in this activity.  The shoulder joint has a bone called the scapula which is present in your upper back. When the scapular muscles are repetitively recruited,  the muscles become stiff , tight , immobile and restrict the scapula from moving freely . When you try to do your usual activities , the scapula finds it hard to move because the structures out there are tight thus inducing pain!

At the moment exercise will worsen pain. Try manual therapy, it gives instant cure.

If Possible i would like to Consult you it seems like you are having pain because of occupational stress and ergonomics, i can correct ergonomics for you and you can feel the difference in one sittin. You can ask for online consultation too