I think there's more to it than that, possibly imbalance of hormones but certainly certain foods, stress etc can make it a lot worse, so I'm told. I was lucky not to suffer at all.
Some, maybe. My wife never suffered with that although she did get queasy and went off coffee for the first few weeks of all her pregnancies. She was only actually sick once, without warning during the afternoon. It was pretty spectacular.
My daughter had dreadful morning sickness, she lost weight but all was well in the end. She isn't an anxious sort of person so I don't think it was that.
Some suffer more than others and there is a name for it which I don't know what it's called but the present Princess of Wales (Kate) I believe was hospitalised with it and my youngest daughter suffered with it for both her pregnancies.