Have you had the vet out? I would get some blood work done and have her checked out soon. It can be so many things I don't want to diagnose. Does she have good gut sounds? Is she pooping and peeing regular? Going down in the stall sounds like HYPP but since she is appaloosa I doubt it but wouldn't rule it out. Anyway call the vet ASAP
"Until one has loved an animal, part of one's soul remains unawakened..."
- Anatole France