Don't know what's happening to the back of my head
So to me I'm thinking several things. I assume you are talking about the spots where you can see the line of your scalp?
It looks like it might be how you sleep. That might be where you rest your head and it is pushing up along that dread section and pushing the dreads apart, showing more scalp. It may also be causing those spots to dread up and get fuzzy making it look like less hair is there.
I would try to switch your sleep position and see if that helps reset that area of your head. Your hair us short so I think that makes it look a little more noticeable.
now that i look at all of them i think you might be on to something
i thought it might need panterra to take a look at it (not that its that severe, just wasn't sure what was going on) i had only looked at 2 or 3 (in an email)
if that is the case .. a couple weeks sleeping differently should tell ya..
if you try sleeping on your side 2 weeks and see no change then we'll bother panterra with it