I had morning sickness during weeks 4 and 5, and was so upset because I figured it meant that it was starting extra early with this pregnancy (with my son, it started around 8 weeks, and let up by about week 15, but it was quite severe). I ended up feeling fine for a few weeks, and then was vomiting for a week recently, and now fine again, and none of it is as bad as with baby #1. So, yes, I found that it can come that early, but don't worry, because it doesn't mean it will last. Hang in there!