I would have to agree that the horse has realized that you may not know as much about lunging as you think. it's quite possible that you are blocking his forward movement by your body position, and at the same time whipping the aire to tell him to go forward. the mixed signals are enough to drive any horse crazy. he reacts by stopping , either becuae he thinks that what your body is telling him to do, or becuase he is fed up, and when you become emotional, with the whip, so does he, and he bites.
I cannot blame you if you do not know how to lunge. no one is born knowing this. you need to ask someone to help you. it's as simple as that. we cannot really help you that much with written word, and to flail around without assistance will only firm up this response from him so that he gets harder and harder, and more dangerous .
So, please ask someone to help you soon, ok? you'll learn a lot and I bet you won't be sorry.