Well I was actually pregnant with identical twins,

and at about 9 weeks I was amazed that I was starting to show already, but I didnt think anything of it.
It wasnt until I got sick at about 16 weeks and had my first baby ultrasound that I discovered it was twins.

So yeah it could very well be twins, or it could be nothing.
I suggest you go to your gp and ask for an ultrasound, they will be able to tell you if its twins or not.

Hope this helps.

I think it's true that your skin is already stretched out from previous pregnancies, thus you will show sooner than usual. But of course, there is always a possibility of twins as well.