When you should do is work in circles with your horse and slowly make the lunge longer and longer so after a while you are a few meters away from your horse. If this doesn't work try doing the same exercise but with a friend walking next to your horse and
Try free lunging in a round pen so that he wouldn't have the pressure from the longe line on his face and give him an excuse to turn in. Also when you're lunging with a lunge line, try positioning yourself more behind him. It will require more walking in bigger circles but it will be harder for him to stop
I had to teach my baby how to lunge, so I feel your pain. What I did was putting him not too far away from me and moving with him, trying to always have his back end in front of me (not too close, you never know) and "chase" him with a lunge whip. Basically he needs to understand that he has to go around you and not towards you. What could help is to put the hand that holds the lunge line behind your back to incourage him to go around. Hope this helps.