help! smoking😩

I found out two weeks ago that I'm pregnant! I'm over the moon. Couldn't be happier but my problem is I can't stop smoking. I've drastically cut down from 20-30 a day to 4-5 I keep thinking I'm doing really well not smoking for 3/4 of the day and then before I know it I've been to the shop, bought cigs and have finished my first one before I realise what I've done. 
Does anybody have any tips to help me? Has anybody gone through the same thing? I hate myself so much right now I'm posting anonymous because I'm so ashamed of myself 😕😕