Probably just the combination of natural whorl and slight thinning that make it look a bit scalpy in your crown.
Most people thin out a bit when they go from late teens to early 20s...unless their name is Zach Effron..
You should go and have a consultation with a recommended surgeon. However, they will all say three things: Minoxidil, Finasteride, and get on with your life and stop worrying!
Oh and trust me, you will care about balding when you are 30, when you are 40, when you are 50...maybe even 60!