Me too! Mine is usually just under my right shoulder blade. I think alot of mine comes from me not being in shape and not having enough hours in the saddle built up yet. The weather's not cooperated much, but hopefully that's changing now.
I usually get sore in my lower back before my upper back when I ride. When I'm on my feet all day, my upper back kills. Like today I was on my feet all day, and now everything hurts.
I get sore under my right shoulder blade too:)
I didn't ride hardly at all this winter. Had some health issues that kept me from riding as much as I use too. Got that all resolved and am now having trouble realizeing me and the horses have lost condition to go for the 3-4 hours we use to do:). But then too, up til now I always justrode one horse. Now I've got to split between 3.
Becky