It's interesting to see the different height/weight/size ratios on here- one pp mentioned being 5'7" and a size 10 at a little over 9 stone (I think)...others saying they are a size 14-16 on op because they have larger boobs at 32GG, or whatever.
I am 5'8 and (pre pregnancy) weight about 10 stone 4 and have huge boobs, and am a size 10. The 5'7" PP would have to gain a stone to be the same weight and that would almost certainly equate to at least 1 if not 2 extra dress sizes.
So I think, OP, the conclusion has to be that everyone is different! No-one on here can tell you whether you are fat or not - and more to the point no-one should. If you feel good and healthy, fine. If you want to lose weight, do so slowly and sensibly and there will be plenty of support on here, I'm sure!
Good luck either way :)