I'm just under 9 weeks and have put on 1.5kgs. My previous pregnancies I didn't put on much in the first trimesters but over 2 and 3 I gained 25kgs each. It was hard work losing it so I'm going to be extra careful this time around.
Don't feel too frightened about your appetite. As long as you are eating 3 meals a day baby will take the nutrients first and then you'll get the rest. If you start to feel out of it, dizzy or faint and you think it is because you're deficient in something just ask the doctor to take your bloods but baby will always get priority with what you put in your mouth. You'll find (hopefully) in second trimester that your intake will adjust to support growing baby. remember - you are not eating the quantity for two, just the quality for two. So you shouldn't be eating much more, just eating healthy so you get enough nutrients for both of you. A lot of women I know actually lose weight during first trimester and the baby grows perfectly.