I Have Pain In My Shoulder Blade That Feels Like

I have pain in my shoulder blade that feels like a pulled muscle when I take a deep breath it hurts under th blade near my ribs it eases slightly with massage but then comes back within a few hours I ha e also used heat rub and this has helped for a few hour
Also it depends whAt position I'm standing or sitting in as to the severity of the pain
Is it likely to be muscle strain or something else