Hi Jess,
I have found muesli bars to be great, but only the ones which are advertised as low GI. ALso Up & Go drinks are fantastic as well as they give you some of the calcium you need when pregnant. I usually have these for brekky when I'm in a hurry, but have used them for morning and afternoon teas as well. Also the frozen meals like Lean Cuisine and Healthy Choice are great as they are portion controlled and have some carbs in them to satisfy those cravings. Also a glass of milk with milo is surprisingly filling and tasty.