Is it normal to masturbate by pulling penis head?

While masturbation I hold my penis head with thumb and index finger and yank it as hard as I can imitating the action of milking a cow. I don't have a foreskin. I tried to masturbate by rubbing my penis, but could not. I also like being tied up by a leash around my neck, especially a chain wrapped around my neck. I also get erection by watching people milking other animals like cows/goats/buffalo's etc. Sometimes I even like to eat my own semen. I just want to know that is this normal? Or something is wrong with me? I even get erection by watching normal porn.