Don't stress too much about the weight gain - plenty of time to lose that after! Main thing is that you and bubs are healthy (having said that, eating healthier & doing gentle exercise is a good thing!). I put on 6kg in first trimester and overall have put on about 20kg. But, I had quite a few bleeds in the first half of pregnancy & kept being put on bed-rest orders, so that slowed up the exercise thing!