Yeah ocd changes theme all the time but typically theres a main theme
Yes obsessions change. The problem is not in the theme of your obsessions but in the doubt itself, you find a more strong doubt you obsess over it.
Core process of OCD remains same, triggering factors may vary, different situations and scenarios
Yes, unfortunately it is. But don't get too hung up on theme. OCD is OCD. It doesn't matter what "disguise" it chooses to wear. Its still OCD and ERP works for all themes.