Hi Eric,
when u quit smoking, you may gain weight because your body is trying to detoxify and the accumulation of water is necessary to flush out all the toxins you have accumulated through the years. this is only temporary. Once you are fully detoxed, you will regain the once beautiful, healthy and fit body you had before you started smoking.
The weight gain is due to the water retention. it will go away after some time. Give yourself another chance. you can do it !!!