I'm sad to hear it's being difficult for you
Don't lose hope yet!
I've read many times that a quick 'check' helps teach them to stop tugging, although some owners don't like using this.
Another method that I DID like, was if the dog is say going too fast, tugging too much, or insists on walking infront of you; stop and tell the dog to sit or lie down. Wait a few minutes until he has calmed down and hopefully this will help.