I feel exactly the same and have the same trouble!  I do think though that giving up smoking will be a greater health gain than being slightly overweight, so I think you should persevere!  From what I hear, it takes a while for your metabolism and habits to even out when you quit smoking, and maybe if you try to reward yourself with a new book or magazine, or a haircut, you will keep motivated.  If you can, try gentle walking or water aerobics maybe to help keep you moving.  Good luck to us!  I'll be thinking of you :)