Mine started mostly at 6weeks exactly. I had had a day or two before the 6th week when I had very mild nausea, but I can say it actually started at 6 weeks. Now it's constant nausea not just morning sickness but I don't throw up. Plus I'm thirsty all the time but never know what to drink as it seems every kind of drink makes me nauseous. And with my DS, I didn;t have any nausea before 7 or 9 weeks, not sure exactly but definitely not before 7weeks.