I am 10 weeks, and still 10lbs less than I was when I got pregnant. I started out with severe food aversion and nausea, and lost a bunch of weight around 5-6 weeks. Since then, I haven't really been eating much until very recently, so when I went to the doctor on Wed. I found that I had not yet gained back any of the weight I'd lost. My doctor was not at all concerned.
It's pretty normal to lose weight in the first tri, even if your morning sickness isn't bad. Food aversions can be pretty strong and keep you from eating, and your body is doing A LOT of work making the placenta and everything (which is also why we're so fatigued). One of my pregnancy books said that right now, your body is working harder just laying on the couch than the body of a runner during a marathon.