Quitting smoking while pregnant.

I have been trying to quit smoking, I am 17 weeks pregnant. I feel terrible when I smoke and I don’t want to do anything to hurt my baby. I have been feeling so much stress having to take my dad to doctors appointments up to two times a week, I am back in school full time, I have a doctors appointment because something is wrong with my feet. What do you do when you are very stressed out and you think a cigarette is the only thing that can help you? Thank you.