Ok everyone, here's what the vet found...the bump is just 1 of several large ones, this big one is right under where the saddle goes...it's been biopsied and it's some sort of allergic reaction. So the vet drew some blood and is testing to see what is causing these bumps to pop up
In the meantime, we're treating it with anti inflammatories and she is now on antihistamines as well, to treat the allergy systemically and stop more from popping up while we figure out what she's so allergic to.
The throwing her legs to the side is exactly what we thought, although not the stifle. She pulled a muscle in her back on the left side, so THAT'S why she was jumping like that. I'm guessing our first few days in the still semi-muddy ground caused that one. So she's on a muscle relaxant and hand walking for 10 days and she'll be good to go there.
Soooooo now I'm starting to take some guesses, what do you think she is allergic to?
The big one on her back popped up last fall, and the rest of them, the smaller ones, popped up more recently -- on her side, leg, back, and even her EAR! Poor girl
I'll let everyone know what I hear back from the vet!