I think these weight gain guides are just that and average or a guide.

I have put on 3.5kg and am 17 weeks tomorrow, so depending on where I read up on it have gained too much or am on track. I am eating very healthily with the odd treat and was about 8 kgs over my ideal weight when I became pregnant. I would check with your OB but like Danni says often it's nothing to worry about.