Have you broken your fast, or are you still fasting? As you will put on weight with pregnancy, just losing a few stone would probably help. I put on 3 stone (36lb) with my pregnancy. And you don't need to eat for two, that is a fallacy lol!
I've been dieting my dog, and i have noticed such a difference in her, more playful, runs more and that is losing a couple of pounds. In doggie terms that is probably like losing a couple of stones maybe!
Just think how much energy you will have if you lose alot of weight, you'll need it with a baby to look after.