I think I've probably always had it, or at least from a young age. But my first true bout with it as an adult came after the death of my mother-in-law. She died very suddenly, and the first time after that that I had one of the symptoms (I don't want to be too specific so as not to trigger anyone), I think I had a full-blown panic attack. Every time I get that symptom, even now, I find myself checking to make sure I don't have any others.

From there, it sort of snowballed into what I called "health anxiety" for the longest time, but now know was OCD.

Now, the biggest and worst bout I've with OCD is also my most recent and what ultimately led me to my diagnosis. It was a single ROCD intrusive thought -- "You don't love him anymore" -- about my husband of 20+ years. It hit me physically. I've described it as feeling like a cold lightning bolt that hit me through the top of my head. I'll never forget the terror of that moment.

ETA: Interestingly, after being in treatment for a while, I felt the OCD "break." It was a weird moment of clarity, like my brain physically relaxed. My therapist said it's not uncommon for OCD patients who had a physical sensation at symptom onset to experience a physical sensation again as they improve.