Does Sky need his teeth done?

I just started riding Sky with a bit and he chomps and chews at it every time there any amount of pressure on it. I started out treating him like a colt and leaving it in when I'm not on him until he stopped. Then I moved on to tying his head around to each side (15mins - 25mins I tried to wait until he stopped fighting but then I felt bad so I switched sides). And asking him to break at the poll. I don't know what else to do he just won't stop. He hasn't got any sores or cuts in his mouth and hes eating just fine (really fat). He never goes to the water trough with a mouth full of hay. Could his teeth need done? Or is it just his habit. How can I tell if they need to be done before I have to call someone out?