I cannot tell you how exciting/relieving it is to hear someone else talk about my compulsion literally word for word. Not sure if it's actually a compulsion, or an obsession, or what it is. But since I was about 12 years old (when I learned to type, coincidentally?) I've counted multiples of three in sentences I read, when others talk, or even just the thoughts in my head. If any given sentence doesn't work out to a multiple of three I try to add commas or change punctuation, like exclamation points or question marks, to make it work out to a multiple of three. I don't pay attention to it when I am actually typing like right now - well, I pay attention but I don't go back to change anything I've written. So basically I can completely relate and I wonder if you noticed when you started doing this, and if it perhaps coincided with when you started typing? I believe that's when I started but I'm not positive.
While it does plague me sometimes when I'm lying in bed late at night, for the most part I'm ok with it - my friends and family just like to pop quiz me about how many letters are in the words that they shout out.
