Im 12weeks and 5 days and I lost weight too. My Dr said it's normal for some pregnancies. Just double check with your Dr your next visit.
Make sure ur drinking enough water
With my first 2 I gained from the start. This time I lost about 10 pounds. I'm now 25 weeks and still down by 1 pound but my OB has been watching me and he's pleased that I have stopped losing and started to even out. He said that as long as I'm holding water and food down and I don't lose in excess of maybe 20 pounds then it is considered somewhat normal. He gave me nausea medication also which I think helped me catch back up.
I havent had any kind of morning sickness, so I know I'm not losing weight for that reason. I get nauseous when I smell something that don't agree with me but have never got physically sick. I am drinking plenty of fluids and always have water with me where ever I go. My friends and family tell me its normal to lose weight before gaining it. I do take walks everyday and I'm not sure if that could have something to do with my weight loss too or not. I'm just concerned because as I said, I have three children already and this has never happened to me.
I doubt that the walking is a contributor. You'll probably stop losing in the next few weeks...I was really surprised to lose weight too because with my others I did nothing but gain. This time I only actually threw up a few times but still lost the weight, so I'm not sure if the nausea meds helped me to not lose more than I lost.