Re: early pregnancy and weight loss
Firstly, it's not such a problem to lose weight in early pregnancy. It's later on that you'll need to start gaining.
Secondly, your 3-5 lb estimate may well be off. If you've been cutting out junk food, you've probably lowered your sodium intake, in which case, you'll be losing water weight.
If you're really worried about not eating enough, try have some healthy starches before you eat protein. Protein fills you up pretty quickly.