I've noticed that where my part is at the top, the line seems to get wider and thinner as my hair gets longer. It's the only part where hints of baldness are evident. (I'm 17)
Lol, at 17 your hardly going to start going bald, especially not where the parting is. If it does happen it will be on the crown or sides of the front hairline.
Nothing to worry about.
It's normal mate, especially if you keep your part the exact same way for long periods of time. You see people who have parts over half an inch wide at the front when they never change it. Its to do with natural shedding and possibly breakage.
Just alter it to either side that suits you to avoid this.
you can kind of deal with it (when you evenually start thinning out if that happens) by parting on the side.
Look at the bright side--if you loose your crown hair no one will mistake you for a female from behind : )
I think when one looks at the mirror for too long, wanting to see something wrong, they will :)
I had this for a long time thinking my hair wasn't growing, and you've probably got the same problem thinking your going bald, when really you almost certainly aren't.
I'd say don't worry about it, at our age it's unlikely to happen.
My part has been the same as yours all my life. I believe you have no worries at all. It is just a natural thing.