What is in my hair(brush)?

My hair gets greasy waaay faster recently. I shampoo my hair twice while showering and then I condition half of my hair. But it’s been getting greasy? I have not changed my shampoo or have been washing it more/less.

Also, I have switched brushes, at first I cleaned my older one as I thought that could be the problem. It didn’t do anything so yesterday!!! I bought a new one. I washed my hair like 20 hours ago, but now the brush looks like this???? Does anyone what could be going on/what could be a solution? Also I dont really use anything in my hair, except for Ouai hair oil once every 2/3 weeks in the ends.