Thin hair shedding in the back

[rint]

I have very thick (in diameter) hair in the back of my head and it's very dark. But if I take a pull of hair from the back, I will get 0-4 hairs that are pretty thin and more blondeish. Some of the hairs are very thin. Has anyone experienced this? I'm not on any medications, only Nizoral.

I haven't noticed this before I started losing hair (about a year).

Thanks