I had twins with my last pregnancy. I found out at my dating scan. I was about 8-9 weeks.
I found out at 8w2d I miscarried tho.
7 weeks 5 days is when I found out.
I found out at 12 weeks 5 days. My forst scanwas at 5 weeks... they said only one. Then next scan at 12w5d it was twins(:
I would think if it was twins they would have been able to tell at that scan however I've never had twins so that is just an assumtion. On the other hand this early in your pregnancy you're not showing, baby is way too small so it's bloating this early on. Congratulations on baby :)