For about the last six months I have had minor to moderate back pain located between my right shoulder blade and spine
How "deep" is the pain? Rhomboid muscle strains/tears/pulls are notoriously slow to heal, and if this is what you've got, it's a hard lick/tough to get over.
You sound like a pretty regular lifter, and if in fact you've done some rhomboid damage (and I'm not shitting you here), you may wind up having to completely re-do your routine for MONTHS.
<------not a doc, but dealt with this. the guy that treated it was a former team doc for the Mavs. He was old, but knew his stuff. Told me that for whatever reason (his theory was that the muscle got a ton of involuntary use in everyday function), it just took longer than most to get over. Prescribed swimming over lifting, amongst other goodies.