18M - Seriously worried about balding crown

Noticed this for a while now, is causing me great anxiety.

Grandfather on my mother's side had a bald spot, uncle has one too.

Dad hasn't got one and my grandfather on my father's side hasn't got one either.

I've been told not to worry and that I'm not balding at all, but my friends think I am. I don't know what to think.

What do you think?