Is it normal to talk to multiple voices in your head?

For as long as I could remember I've always talked to these two or three voices within my head. They don't tell me to do bad things though, just good things. Though sometimes they call me stupid or an idiot. I can't do it willingly. It always happens unexpectedly. I never talk out loud just inside my head with them. I sometimes even look to my left or right like there's someone that should be there. They even control my hands and force me to punch myself. Am I insane? Is this normal? Should I see someone?