7 Weeks - Large Yolk Sac

So yesterday I called my ob to see if I could get something for nausea. I have been getting really bad the last two weeks. I had dropped almost 10 pounds during that time frame despite only throwing up a few times. They ask that I get in the office within a hour for a checkup. I see the NP and she gives me a prescription for Diglecis. Last minute she decides to do a u/s. It takes a bit to find the heartbeat. At the end the tech said that my yolk sac was large. She said that at my 10-week checkup I need to have another u/s. She said that she is 90/10 sure there is just one baby, but this early on that there could possibly be another in there. (Neither sides of our families have twins except in a case of a cousin that did invitro.) Of course, I do the stupid thing of looking up large yolk sac on Google. It seems that most items I found were forums not articles. Most were sad stories about how people will miscarry or more likely to have chromosomal defects. Please tell me there is hope for a healthy pregnancy! It took us 10 months to get pregnant this time.