Try not to worry too much. I did SW albiet half heartedly on and off through my pregnancy, but was eating ALOT of unhealthy stuff as well. I had an addiction to cherry tango and my last dinner before I had my son was a dominos stuffed crust! Funnily enough it was also my first meal when we got LO home (not THE same pizza though!).
I put on about 3.5 stone in total. My son was 9lbs of that! I then lost about half of that without really trying and lost the rest dieting (although not with SW) by the time LO was five months.
So don't worry about what you put on while pregnant cos you can lose it afterwards!