i only have GD, and haven't had problems with nausea, but i thought i'd write down some carb/comfort food items i've discovered i can have without tweeking my blood sugar too much. i know each woman is different, but maybe some of these will help.
i have found that if i eat whole-wheat pasta with white sauce and cheese, just in a moderate amount, i usually do alright two hours later. i have tried this with red sauce and that doesn't work for me! so i've been making a lot of white sauce whole-wheat pasta casseroles with plenty of cheese. this has also worked when i go out to eat at the Olive Garden, for example. as long as i get their whole wheat pasta with white sauce, i'm okay. i've also found that if i eat a salad with it, it helps me fill up better and thus keeps my sugars down. i was like you and didn't have to worry about sugars or portion size before this, so limiting the size of my meals has been a big challenge.
other comfort foods i've turned to are sugar-free pudding, sugar-free cool whip, and sugar-free ice cream. i've had to really read labels though because with ice cream especially, there's a great variation on the number of carbs that they contain, even the ones labeled sugar-free. same thing with cereal. i found that honey nut cheerios has way less carbs than granola.
as for gaining weight, i try and eat a lot of eggs (whole eggs, not just the whites). this helps with the protein too, but might not help if you're nauseous! avocados are a good, healthy source of calories. a woman in my expecting board also told us that greek yogurt has much fewer carbs and higher protein than regular yogurt, and she's right--even the flavored greek yogurt has far fewer carbs than "light" Yoplait. you can probably find some full-fat greek yogurt, which will help maintain your weight.
the other thing that might maintain your weight and help with the sugars is meat. this isn't an option for me since i'm vegetarian, but the few times i've cheated i've found i can eat a bigger meal if it has meat in it, and my sugars turn out beautifully.
hope you find some stuff that works for you! best wishes.