Don't forget we carry excess fluid too. Some carry loads of amniotic fluid and others just under the average. So as the average guide of weight gain chart is shown, it's normal for some mothers to carry a smaller amount than average.
There are pregnancy calculators online where you fill in your details and it works out an approximate weight gain chart.
Don't hold the calculator gospel!! There are loads of reasons as to why some people are either above or below the average. As others have mentioned, providing you do things in a healthy way that's the main thing.
My friend was tiny all the way through her pregnancy and looking at her, you'd think she was 1 month behind, her final 5 weeks, all this weight came from nowhere!
It's perfectly natural to feel concerned, book an appointment with your dr/midwife, they should hopefully put your mind at ease x x x
Okay so. This should also be posted in the Teenage pregnancy part only for the fact that I'm about to turn 15. Other than that... The title basically explains it. I'm at about 25 weeks or so (I believe. I lost track) and i've gained about... 16 lbs or 18. I'm just curious if this is a good thing or if I'm gaining too much weight too fast or if i'm not gaining enough weight. I was a healthy weight before I was pregnant if that helps. I'm not sure this is serious enough to schedule a special appointment with my doctor yet so. Please help just in case it is so I do it in time. Thanks a bunch! 
