I didnt put on any weight during first tri (i was soooooooooo sick). Since 2nd tri I have put on about 2 kg i think, but coudlnt be so sure as we dont own scales. It sounds like you were particularly sick with morning sickness so maybe your body just had the chance to get that extra weight.
Eat what your body needs! if you crave something eat it, but obviously you would have to eat fruit and stuff too.