Skullyfrost,
Don't be too hard on yourself. Practice makes perfect. You'll get use to not smoking in the car, it just takes time. Where are your distractions? Some members have found good music, sunflower seeds or sucking through a straw helpful.
With regards to your antidepressants, be sure to keep in close touch with your MD. It's quite possible your medication will need to be adjusted once you quit smoking.
Danielle, Bilingual Support Specialist