Stop lunging or roundpenning him. Control his head at all times with a leadrope or reins. Catch him, tie him, groom him, tack him, ride him, tie him, untack him, groom him, let him go. That's it. If you want more bonding, handgraze him on the lead. Be completely businesslike for a few months--he's got a job to do, make him do it. Don't give him a chance to rear at you. He's either on a leadrope being led or tied by you, or he's under saddle and bridle being ridden by you. Control his head at all times. When you've gotten your confidence back, and he understands that you are boss, you can move on to other things.