How about I eat my scabs and my own dandruff!
That is disturbing to envision. Why do you eat your scabs and dandruff?
I want to stop this habit. It has been going on for a couple of years.
It's disgusting that you eat your dandruff and scabs. It's unhealthy and weird. You should treat your hair with anti-dandruff shampoo.
This is disgusting and I know it, I hardly have any dandruff though.
It's good that you have acknowledged that eating your scabs and dandruff is a bad and disgusting habit. Now you have to take the steps to change this habit.