Hello there!
This is a very common problem assosciated with a bad posture. Along with the pain between your shoulder blades you might also experience some tightness in the trapezius muscle ( the one that runs from base of your skull towards the shoulders on each side )
This commonly occurs as we sit with a very bad posture throughout the day since months or years , it has caused repetitive injury to the paraspinal muscles overtime and now when the muscle is too weak to perform it's normal task, it is overworked, tired , damaged & has started hurting .
Next Steps
Since it is a chronic pain I suggest you to go see a nearby Physiotherapist.
°The first goal of the therapy is to reduce the strain on the muscles.
°This is done by taking Manual therapy (spinal adjustment ), Electrotherapy ( to relax the strained muscles & to accelerate the healing )and Ergonomic advice and advice for workstation adjustment .
All the above things will be better explained by the Physio in person
This will take 10-15 sessions to heal.
Health Tips
Please note:
1)Take hotpacks 5-6 times a day, along with Physiotherapy to keep the muscles relaxed as much as possible to enable a fast recovery.
2) Don't start with exercises right away. Focus on reducing pain to 50% of what it is now and then start with exercises.
It doesn't matter if you start exercises a few days late but if you start it prematurely it can delay your recovery & increase the no. of sessions. Remember when you are sick you take a break and rest It out , you don't go to the gym to workout! Right now your muscles are 'sick'!
3) It is very crucial to follow ergonomics & do workplace modification to avoid aggravating the condition and prevent future occurrences. The physio will guide you with smart & inexpensive modifications. You don't need to buy something special for it.