Hi there!
Having never been pregnant I'm probably not the best person to be answering, but I do work in an office with a continual stream of pregnant ladies!!
I do know that a few of my friends have had practically no morning sickness at all in the first 5-6 weeks, only to have it hit with vengeance a few weeks later! One girl does have a few good days, only to spend the next week vomiting!
I guess the important thing to remember is that every pregnancy is different- some sail through with no issues, while some vomit for the whole nine months!!
Good luck!