Thank you all so much.
My OB called me the yesterday and told me that there were two yolks in the scan, I've got to wait an extra week for another scan but he believes there might be twins. yikes!!!!!
So, i've decided not to stress, I'll just wait and see what happens, there isn't a lot I can do regardless. So i'm staying healthy eating lots of good food what will come will come of it's own accord and on it's own date. Had a chat to my mum and she carried me and my sister to 44weeks, I turned out fine, as did my sister. So perhaps we just have a longer gestation than others.