I wish you could upload pictures on here.
As it is still early, I'm holding out serious hope for two sacs. I'm no doctor, but I feel like when I look closely at my first ultrasound (5 weeks 2 days) I can see two yolks. It's almost hard to see, but it looks like it is behind a membrane... Like they are sandwiched one on top of the other and that's why it looks like one. Anyway, all I can do now is pray to able to accept whatever is ahead. Good luck Tanjat keep us posted, and thanks geekmom & new2thia.
Was there one or two yolk sacs? I think that its still too early to tell for sure if they're mo-mo or in fact mo-di. Im kind of in the same boat...my twins share the same gestational sac but each have their own yolk sac which I read usually indicates that they'll have their own amniotic sac but that they'll still share a placenta. Im terrified that it'll be mo-mo as those are the highest risk.
Momos as you've probably already found are incredibly rare and incredibly high risk. It's possible there's a separating membrane between the embryos that they weren't able to see in your first scan - if there is, that would be wonderful and decrease the risk significantly. But all you can do at this point is watch and wait and hope for the best. I have a friend who had a terrifying journey with her momo twins, they ended up with the craziest cord knots you could imagine and were delivered at 32 weeks weighing less than 2 pounds each. But they were fighters, they survived and thrived and started preschool today. It's very scary. Search for support groups - I know there are at least a couple of them on Facebook - and keep a positive outlook... I wish you the best of luck.
Congrats! Finding out your having twins is so exciting.