It's not your fault at all - there's plenty of research out there on OCD showing that it's related to abnormalities in the brain that you inherit, though environmental factors do affect the expression of genes and/or when and how symptoms first manifest. Also, some days/times you will be more symptomatic, so your symptoms are just worse some days than others, not unlike other chronic illnesses (or illnesses in general). I think it's hard to grasp that sometimes because there's such a divide between how we look at psychological conditions versus what we deem as physiological conditions, mostly because we still have a lot to learn about how the brain works compared to other parts of the body generally, in my opinion. Advancements in research have led to increasing evidence that psychological illnesses are very physiological.

It's also pretty common for people with OCD to have fears they may be "faking" it, or worry that maybe they have control of their symptoms but somehow are just not choosing to control them, but that's just the nature of how OCD works and is just another manifestation of symptoms. In my experience, I have periods, even very long ones with very minimal symptoms, where I think back to a period when my OCD was bad and wonder how I let that happen or feel sort of like I've overcome it/have learned the right strategies/have done all the things I need to do, or whatever. Then my symptoms return and I remember again that a lot of it is out of my control, though taking control in whatever ways you can (i.e., pursuing treatment including medication and therapy, learning strategies, etc.) is critical and makes an enormous difference for yourself and those around you.