Twin Pregnancy

Hi all
I found out I was pregnant with twins when I was 5 weeks and 4 days pregnant, they said it was twins but couldn't see a yolk in one of the sacs because it was possibly too early, now it's all I can think about and I don't have another scan until I'm 12 weeks at the beginning of March....has anyone experienced this??
I definitely feel like they are both still there as I've put a lot of weight on already and I'm feeling sick and exhausted all the time (now I'm only 6 weeks and 4days pregnant)
Thanks