“Pure O” is no different than any other OCD theme. You deal with it in the exact same way you would deal with any other OCD symptoms: you accept the stuff in your head, don’t engage in coping, checking, or controlling compulsions, and then you do things aligned with your values.
When you’re seeking help, I also recommend being open to the possibility that you don’t have “Pure O”, that you have OCD, and it’s just that some of the mental compulsions bother you more, which is why your focus is on the compulsions in your head.
Overcoming OCD requires making changes throughout our lives. We’re often engaging in many compulsions that we think are totally normal but are actually causing OCD symptoms we really dislike.
Focusing only on a narrow definition of our symptoms can become a barrier to recovering. We can start to seek out the “right” way to recover, similar to other compulsions we might engage in to feel or do things in a certain way because we’re afraid that not doing it the “right” way will lead to something bad happening. But that’s a compulsion. Trying to do recovery perfectly to avoid relapse is the practice of OCD.