My Rog has been tapering down on smoking through use of the prescription drug "Chantix." He is just finishing his third or fourth week, can't remember, but he has gone from at least a pack a day since age 16 to maybe five or six individual cigs per day. The med. blocks the nicotine receptors, so you gradually get nothing out of smoking a cigarette. I imagine it would do the same for the gum, i.e. help you get off the gum.
Other than that...titrate it down, if you can, as Amos has said. If you can get past the intense first minutes of a craving, then go for something else, i.e. cough drop, regular chewing gum, etc. then it might get easier. I have read though the nicotine itself is more addictive than heroin, so this may not work as well as the prescription.
Good for you, for stopping the acual cigarettes, though!