If you were overweight before you fell pregnant you are not meant to put on any weight before around 20 weeks. I was a little overweight when I fell pregnant and lost weight for the first tri then gradually put it back on til I was back at my pre pregnancy weight at around 18 weeks. I then started to put it on and ended up 15 kgs heavier than where I started out.

A week after I gave birth I had only about 3kgs to lose to get back to my pre pregnancy weight. Based on all that I think you have nothing to worry about.