Undecided Question

My hair is just slightly thinner on top?

Im a 21 year old white male with a slightly mature hair line, like in between Norwood 1 and 2. Its been that way for a while since like I was 19 so Im not terribly concerned about that. Ive grown my hair longer than I usually do.However, I feel like my hair is slightly thinner on top of my head than on the sides. My mother who works in skin care said it doesnt look noticably different than it used to be when I was younger, and my GF says she cant see it. However when I look in the mirror I swear it looks thinner on top than the sides of my head and it also feels thinner to the touch (id take a picture but it isnt significant enough that you guys would see anything). Maybe its all in my head, im not really sure. No one on either side of my family is bald (at least until they reach old age). I figure I should probably check with a dermatologist, but I was just curious if anyone had thicker hair on the sides than on the top.

Side note: Im not a terribly vain person, if I bald Ill just shave my head, i usually rock a buzz anyways and look pretty good, im just curious.