It’s fairly common for people who are trying to stop ruminating to get stuck trying to figure out how to stop. They start ruminating about how to stop ruminating, or in other words, trying to figure out how to stop figuring something out. It’s like trying to clean yourself with dirt.
Don’t ruminate about how to stop ruminating — just stop, and if you need some tools to help you, see How Do You Stop. And don’t get hung up on whether or not something is rumination. If you think it’s rumination, stop; if you’re not sure, take your best guess and either do it or don’t do it, but don’t get stuck trying to be certain.