I am pregnant with Bubs no.4 at the moment and feeling huuuuge!

I kept pictures and measurements of my waist every month throughout my other pregnancies and they were all roughly the same (within a cm or two). This time I am measuring at what I did with 3-4 months with the others and Im only 6.5 weeks!!! I'm concerend that it might be twins (not as much as my husband though!). I dont think I have actually put on that much weight - just a whole lot bigger around the belly

Any ideas?any thing else that might be causing this? It just seems odd to be almost the same with three and then massive this time!

Thanks