don't sweat it mate! I'm 23 and have been getting thin in the hair department since I was about 15 or 16. It used to worry me so much, the hairdressers would just I had a ' double crown ', what ever the fuck that is! It's more annoying because from the neck down I am the hairiest mofo ever, it's like a forrest on my back and shoulders! I've often thought about shaving my back and shoulders and sticking it on my head LOL!
Anyhow my is don't worry, so what you might be going thin, does it change the person you are.....I would hope and suspect not, so just try and get on with it.