I agree with a salicylic face scrub but St. Ives can be a little harsh due to the amount of grit in it.
I currently use BeeBald "Clean" as an exfoliator. Very little grit, very mild scent, and it works.
I had a similar issue a while back, though not as bad, and had a little trouble getting rid of it. Once I started using the BeeBald products my head totally cleared up in a week and I haven't had the same problem since.
Not affiliated just a big fan.......
www.BeeBald.comAlso, if that is only on the side of your head that you sleep on... try changing your pillow case a bit more often. The oils, etc. that you are leaving on the pillow case could be a contributing factor.