No Sperm count

We have been trying for a baby. First i was operated for fibroids and thought all is now well.  But i noticed no sexual interest from my husband untill i asked him to alos go to a male Doctor, and he was found with no sperm count at all. He was put on 6 months cure and it helped his count went up to 8. But still during this time he still did not show/interest in sex. Eight months later his sperm count went down to 2. What could be the problem with him. My husband is a chain smoker and is try to stop now. Will stopping smoking help in restoring his sperms back or its too late, if so what can be done to help him. Is there chance that he could be a dady he is 43 yrs. Confussed please help.