Repeatedly checking to see if my door is locked (within a span of about a minute, about ten times, walking down my walkway and back (when I was younger)), washing my hair constantly in the shower (not allowing myself to leave without doing so), having to ensure that every single little toy I own does not have any quality control issues, which includes any form of warped plastic or slightly bent/strained plastic, not allowing myself to sleep at night without constantly checking to see if all 7 cats (they hide a lot, too) are inside my house, having to wash my hands before not a single mark is on them, etc.
However, yes, I was diagnosed by a professional. Yes, I take medication for it. You do not see me using it as an excuse for anything, though. I use it to portray why I don't finish many projects, but I do not simply throw all of the guilt on to a disorder. I am aware of the problems and I am making a solid attempt to overcome them. No, I wasn't aware that I had it until I saw someone for it. It was about 6-7 years ago, too.