Looking back, I now realise I had some OCD tendencies as a child. I used to bounce my legs in a rhythm, and found it really difficult to stop, like if I didn't finish off the pattern I would feel really stressed about it, and I used to find it hard to actually find an suitable end to the pattern, they just wanted to on after the end. I also used to do a similar thing by tapping my teeth together.
I realised it was strange when I was about 8, and made a concious decision to stop doing it, and that pretty much worked I guess. Now, I just get fixated about putting ornaments on tables in an even manor and sometimes go a little OTT on cleaning things that dont really need to be cleaned lol, but it doesn't control me.