I got my morning sickness at week6 and it came on VERY suddenly. Felt fine at about 2pm and by 4pm felt yuck. Felt yuck till week 12 and it finished almost as quickly as it started! I still felt tired and crazy hunger for the rest of the pregnancy but didn't feel sick again. Luckily I didn't throw up - just felt awful which i think is just as bad. Like having a hangover constantly but without havng the fun of having a few drinks the night before!