I was going to say it could be Psoriasis or maybe Seborrhea

If it's causing you pain, or is really really annoying, you should go see your doctor about it. There are prescription and over-the-counter treatments, but a doctor would be able to tell you what it is and then either prescribe something, send you to a dermatologist, or could tell you which OTC treatment you can use.

I cant remember if I had psoriasis or seborrhea, but about 20yrs ago I had one of the two, and my doctor told me to use an OTC shampoo called Neutrogena T-Gel. The active ingredient in the shampoo is coal tar, and the shampoo doesnt smell all that great, but it's great for calming down the itching from both scalp problems. It gets rid of dandruff too. I used to use it all the time, but it's kind of tough on color treated hair, so once whatever I had back then calmed down and seemed to go away, I quit using it.

Thinking about starting to use the T-Gel shampoo again. Our local water has been extra hard lately because of all the junk the utilities district has been putting in our water because of all the flooding here. (we also havent put salt in our water softener here at home lately because the bags are too heavy for us to lift) My scalp is starting to get mad at me.