Tightness and pain in shoulder blades Heart or Covid?

[Zaramac1]

Hi I was diagnosed with HF And AFib I February this year and am being treated with a cocktail of drugs which seem to be working. Unfortunately I had a tummy bug straight after. And then I got covid in March.

I was experiencing a severe pain in my right shoulder but the doctors at the hospital couldn't find anything except my bloods showed infection. I was sent home with 2 kinds of antibiotics with which I had a terrible week ( diarrhoea nausea thrush ulcers in mouth) after which the pain subsided but I was left with sore mouth and very little appetite.

Since then the pain in my shoulder blades is now like a tight band across my back. Had more tests last week but all OK.

My question is Could it be long covid or my heart causing the pain?

TIA