dandruff causing skin issues

I recently got a hair cut. I had really long hair now they are shoulder length. Ever since that haircut my hair have started to shed a lott more than they previously did. I also have dandruff , its not flaky but dust like and makes my scalp superrr itchy which i think is making my hair fall off even more. And due to that dandruff my forehead has gotten little itchy bumps , they arent like pimples but very tiny little bumps like this . I dont know what to do with my hair and forehead . i really need help.

I use nyle dandruff shampoo and loreal's conditioner and oil my hair whenever i can. my oil includes oilive oil, castor oil , vitamin e and tea tree oil drops.

thank you