Well. I still don't know if this will work for you but my top tip for OCD (which I have also tended towards all my life, though never had it really badly) is to think of it like this.
OCD is like a religion (and indeed I think it comes from the very same part of our brains). I know you like me SGB are an atheist with little time for superstitious nonsense, but think about it - you do OCD type stuff because you convince yourself that "If I just do xy and z, I can make things OK" or "I will feel safe if I have done this or that routine". Of course it never does make us safe and so we tend to come up with more beliefs and rituals that we have to do.
My trick is to remind myself that these compulsions came from me in the first place - I made them up. So I can make up more rules, and those rules can include dismissing the rules that are making life difficult. So for example if I fail to do something I "should" do, eg checking something or worrying about something, instead of panicking I make up a new rule - eg I'm allowed to not bother at least twice a week. If I find a need to ritualise is taking over, I make up a rule that it's time that ritual was cancelled. In this way, as fast as they try to accumulate, I turf them out. It gives me a nice feeling of being in control too (which is what OCD types actually want) instead of feeling controlled.
It might sound as if I'm twitchingly bonkers thinking about all this stuff all the time, but in fact this is second nature now and, while I am still very much a do-it-all, organised type of person, I'm actually fairly relaxed in general. I can see completely how OCD can take over people's lives but I feel I can keep it at bay if that makes sense.
I said "-ish" however because I still am generally way too much of a worrier - but I think I have just learned to live with that. I try to laugh at myself and distract myself with mindless trash. I love magazines like Ideal Home and Red even though I think they are shite - they have the power to wind me down, especially with a bath. If you can. find something that works like that for you.