Comparing hair from the back of the head to the top.

[drgrant]

Sounds like you may be more paranoid than actually have reason for concern.

First, I have found with a lot of people as well as myself that the hair on top of the head is thinner than around the sides or back, regardless of whether they are losing their hair or not. Even when I was younger this was the case for me, and on many women as well, the top of the head is thinner.

You say that your hair is blonde and fine, but that there is a lot of it. That means that even if you were thinning, it wouldn't be too noticeable. Even if your hairs get replaced by thinner and thinner strands, you will still probably have a lot of hairs, it will just look like very fine hair.