Dude I'm not alwas in the mood and I'm 19! Theres nothign to worry about unless you can't ever get in the mood with some enticeing on your partners part, then you might want to look into seeing a doctor about depression, I think you talked about maybe being depressed in another thread. If you are depressed don't do what I did, last year I became completely noctournal and didn't talk to anyone, not even close friends parents or my girlfrind about it, I ended up not registering for class and having to take the semester off. It'll fuck up your life for a good long time, talk to a friend or somethign if thats the cause.