Hi H.,
I think everyone at one time or another has a touch of OCD. I used to count steps into my apartment, at 11 and still at 17, and everytime I visited my mother until I was 21 - there was 13, I'm 37 now and I still remember.
I also counted blocks of cement in the sidewalk on my way to the bus stop and would never step on the cracks. I couldn't talk to my friends unless I walked in the street or on the grass - I was too distracted with counting.
I eventually grew out of it, without medication. I'm a little off my rocker sometimes, but I also have 4 kids, with my oldest going into college in a couple weeks, and a little one almost 3.
Why don't you talk to his doctor, let him listen to his breathing, maybe he has allergies, or humidity is effecting his breating? It may be a simple fix. Remember, you do have the option to say no to drugs that may be perscribed, for ocd, adhd or anything else.
If there is nothing physically wrong, maybe something social. Friends doing something that he knows is wrong? Is he around someone he is not comfortable with? too many people, someone not paying attention to him? (I don't mean you or anyone in the house, maybe he has something to say to someone, and doesnt know how to get their attention - it might make him nervous, without knowing it)
Good luck