Sorry to hear it's being such an uphill struggle, DDD. I'm with busywend on this one - although it might seem unwise or over-ambitious to diet at the same time as giving up smoking, I think being careful with diet and exercise - lots of walking!! - is more likely to boost your confidence in the longer term and keep you on the track on non-smoking than overeating or eating junky foods... which will make you depressed as you gain weight, which will make you want to have a cigarette... been there done that!
Keep telling yourself how well you've done to get this far, don't allow yourself to do something you'll regret (starting again) and take to them there hills with some stout walking shoes!! Best of luck.