Broken bone delayed healing

Patient: Over six weeks ago i had a lateral malleolus fracture, broke through my lower fibula at an angle. I have been immobile, with a cast, getting x-rays every two weeks. the doc says my bones are all lined up, there just has been no sign of bone growth whatsoever. He put the aircast on me yesterday, and i am unsure if that was the right thing to do because it is quite painful now. I understand that smoking is bad for the healing process, so i am quitting and down to two-a-day. my question is could there be something else wrong with me that would delay bone growth, and is this normal?

Doctor: