So for about 6 years now from like 7th-12th grade i've had this discloration brownish look down the mid part of my spine, with red lines going across my back (about 7 of them) it looks like this:

( ---- o ------)
( ---- o ------)
( ---- o ------)
( ---- o ------)
( ---- o ------)

some info on my background, I have terrible posture and was always sitting horrible in those metal chairs, also I had been sleeping incorrectly all that time slouched up with my back bent. I also don't get much sunlight due to the fact that I work on the computer all day.

Now getting out of highschool last summer i've changed the way i've slept, the way I sit, the chair I sit in, all to proper ways and i've noticed it is starting to lose color. Also when I wake up from sleep now it is almost entirely gone, i'd say 85% of the weird coloration is lost.

My question is really if anyone has any idea what this is or would cause this, and if i'm correct in assuming bad posture and incorrect sleeping caused this. In all this time it's never hurt, affected me in anyway, or gave me problems. Any help or comments would be greatly appreciated cuz im stumped.