definitely split your meals into small meals, rather than take big meals... another way to alleviate morning sickness is to not have your stomach totally empty.
i just went to see my gynae today and consulted her regarding my morning sickness problem...
in my week 7, i was throwing up once every 3 days, once a day.
in week 8, i was throwing up once every other day, once a day.
my gynae say this is 'normal' or 'average'. (but i'm already feeling so terrible!)
back to your qn... my gynae said that vomiting becomes dangerous if you're dehydrated, then you'll need to be hospitalised and put on drip. so even if you can't keep food down, must make sure you take liquids (not necessarily water, but any form of liquid.)