I don't want to get disfellowship
Voluntarily confessing to a couple of elders that you are smoking seems to be incompatible with that desire.
That said, the cat's out of the bag now.
Your only hope would be to convince them that you are "truly repentant". This would involve lots of crying, appearing to utterly gutted about your "damaged relationship with Jehovah", expressing a strong revulsion to smoking and vowing to never do it again, and generally sniveling like a puppy caught with a half-eaten sausage in its mouth.
You mentioned you haven't attended meetings in a long time, so your act would have to be Oscar-worthy.
Good luck, sounds like you will need it.