I was the same way. I'm 21 weeks now and am just starting to put weight back on. I'm STILL vomiting...
If you have morning sickness, then yes its normal. I lost 15lbs with my first pregnancy. I'm currently pregnant with my second and lost a total of 11lbs. Your baby doesn't need much food in the early months...mostly just folic acid! I wouldn't worry much unless you feel you are really underweight. Maybe talk to your obgyn and see what they say. Best of luck!
Do you have morning sickness still? I lost a weight until I got my morning sickness under control. Then a few weeks later I finally started putting on weight very slowly.
Try counting your calories to make sure you're getting enough. I was shocked I eat the bare minimum of food some days. And I love my food.
Maybe try adding some extra proteins in and, talk to your OB or nutritionalist. My OB has a trained nutritionalist on staff and at my 12 week apt I had to have an hour apt with her and she checks in every month or so and was there for Any questions about eating healthy and enough even lost birth when I wanted to bf