Why do I have a tendency of doing these things?

I have I think a slight case of OCD. I have to have everything perfect books or hangers facing the same way. I can have stuff cluttered but it will literally stay on my mind until it is done. I have to do some stuff a certain number of times or do it just right or I'll have to keep doing it. That and ever since I was little I make repetative noises. I'm not trying to be rude or annoying I can't help it or I don't realize I do it. Clearing my throat is one, sniffling is another, making other random noises like one for awhile was a pst noise. Sometimes just when I am nervous but it annoys me that I do that. Is that normal or why do I do that?