I COMPLETELY agree that something is definitely causing this and that it's important to find out the cause. I'd worry about that first and foremost.
However, it's important to be safe, and if you're an eager horse person like me you're going to be back on her soon anyway. So if you ever find yourself in that situation, you need a tool to deal with it. Rearing can be incredibly dangerous. Watch this video. I think it might help you.