I can so relate to so many of your experiences; Tunnocks and isshoes especially yours.
In my case, my OCD is focused on issues around health anxiety and intrusive thoughts around the fear I will die and leave my children without a Mother. At my worst, I was housebound for days/weeks on end, photographing and cataloging every inch of my body, categorising and labelling the pictures to check for any changes to moles (of which I have over 300), my skin, my hair, lumps/bumps etc. Once I'd done all this (which you can imagine, took a long time) I'd start it again and see if anything had changed (which of course, they would not have in such a short period of time). I then decided I hadn't been thorough enough and bought a microscopic camera so I could photograph all my moles in more detail, for example. I have done similar in fear of many other conditions (e.g. breast checking hourly for lumps or changes, for example....).
My psychotherapist and psychologist refers to OCD as 'the checking disease' because we're all concerned with the need (the compulsion) to check something ISN'T happening (e.g. the need to check someone will stay safe, preventative courses of action etc.). They also made me understand that OCD is mostly prevalent in people who are generally extremely empathetic and caring; it is a disease that focuses almost exclusively on the prevention of, or the fear of, something bad happening to yourself (which would, in turn, cause hurt to your family via grief etc.) or someone else, which is driven by OCD latching onto the empathetic nature of a person.
CBT and EMDR has helped me enormously but I know now that this is not something that will ever go away, merely something I can control as best I can with hard work, practice and self-regulation, but I live in constant fear of the next relapse.
My psychologist also, quite rightly, helped me to understand how OCD acts as a bully. So, you may get one facet of your compulsions under control but the OCD will try and bully you in other ways. For example, last year, I'd been managing it really well and felt prematurely confident that I was 'sorted'. But triggers can surprise you and they catch you unawares. One morning, I woke up and quite simply realised I couldn't clearly remember getting into bed the night before (as in, with any specific detail; had I put my pj top on first or my bottoms? Had I brushed my teeth before washing my face or the other way around?) I became fixated on the fact I couldn't remember it clearly and then, suddenly, a tidal wave of anxiety hit me and I became completely convinced I must have somehow done something dreadful which my mind had blocked out. I started to believe I must have left my DH in bed, and gone out to a bar, met someone and been unfaithful, which would have ruined my marriage, so I decided my mind had blocked it out. At the time I couldn't see how ludicrous this must have sounded to him (seeing as I had been lying in bed next to him for the whole night) yet I was convinced I had broken up our marriage yet couldn't remember. Again, OCD latches onto your absolute worst fears, and drives you towards trying to ensure they don't happen, or becoming convinced that they somehow already have. You can also start to seek for evidence of things that HAVEN'T actually happened (e.g. the poster above who had to check she hadn't run someone over; very, very good, albeit heartbreaking, example of an OCD event-obsession). You can become obsessed with finding evidence of something that doesn't actually exist, therefore, the cycle can never end (because you can't find evidence/proof of something that hasn't happened). This was probably my lowest point as I was suffering with not only the intrusion of worrying what I may have done but the sudden realisation that I would never actually be free of OCD and it's control. It was absolutely terrifying, but in hindsight, prompted me to take a more aggressive course of action via psychotherapy so I have to be grateful for that.
I find it quite hard when I try and explain to people about my own experiences with OCD (which I still find very taboo and very hard to do) that people don't really 'get' it or, dare I say it, even 'believe' me simply because I don't wash my hands until they bleed and I don't have to check I've turned the oven off twenty times before I've left the house, or ritualise constantly etc.
Really interesting reading on this thread and I really appreciate those of you suffering taking the time to reply with your own experiences as I've not spoken to many sufferers IRL. Makes me feel much, much less alone - thank you xx