Weaning yourself off nicotine is a gradual process, and there may be times when you hit rock bottom, lose all motivation and just want to cry. This is quite common: tobacco is an anti-depressant (and has been used as such for many years), so stopping can leave you a bit down.
If you are suffering from depression, your doctor might be able to prescribe anti-depressants. Don't think too much of taking anti-depressants if there's a need: 2-4 months of treatment won't make you addicted to them and could be the best thing for you in the long run. A lot of smokers start again because of depression, and once you've got so far it's such a shame to give it all up just for a cigarette. Focus on how well you've done to get this far, and take each day at a time, because tomorrow will be that little bit easier. Before you know it, you'll have stopped wanting to smoke.