Nooo too big too early!! My mum started showing early but come on...
I wouldnt worry about it too much, Luna-baby. We all carry in different ways. I carried small with DD- so much so that the doc thought my placenta wasnt functioning and sent me off for an emergency scan at 34 weeks! Even when she was born he said that in his professional opinion, she doesnt know where I kept her!
You could also have a bit of bloating and gas that makes your tummy look a bit distended. I still think you look gorgeous though.
I think I will take over from everyone in terms of tummy size as the twins get bigger!