I haven't weighed myself, or been weighed, for at least a month, and when I last did I swear it hadn't gone up since about December time. Strangely enough, weighing women isn't part of routine antenatal care here anymore, and I have not once been asked to step on the scales whilst pregnant (and I've had full, standard prenatal care plus some extras due to scares of various sorts). So, I guess they just don't think actual weight matters much? As long as your belly is growing as normal, I would think it's alright (had a bit of a worry last week as my fundal height appeared to have shrunk, but at my follow up today I've put on 2 cms in a week, thank goodness!).
So, based on the fact that weight isn't even considered relevant in this country (not that this country is always right but it aint too backward!), I'd guess you shouldn't be worried if everything else is OK.