I gained like 8kgs in the 1st tri (I didn't vomit and cause I felt sooo bad I ate! Only thing that made me feel better) but then between like 18-26 weeks I didn't gain anything at all!! I think maybe like 200gms or something! I def was getting bigger and was concerned that I wasn't gaining but my MW said it was fine and that really it is only in the 3rd tri that you "should" be gaining weight... but pregnancy is so individual! Every single mother is different!!
I wouldn't be too concerned unless your belly wasn't growing etc...

I think there is too much emphasis on weight in pg anyways, it ends up stressing us out, are we gaining too much, "I've gained more than the normal 11-16kgs", are we not gaining enough, in the end... just make sure you're eating enough for you and baby, and that you are getting all the vitamins, minerals, calcium etc and don't focus on the numbers on the scales...