Hi, I Had An Ultrasound Today, Iam 6 Weeks Four

Hi, I had an ultrasound today, iam 6 weeks four days.. She said there was some debris in the fetal sac next to the yolk.. We saw a tiny flutter which we thought was the heartbeat but iam concerned about the debris.. What does that mean? She seamed concerned as well.. I was too scared to ask her about the debris at the time.. I go back next week, but I can't wait that long to know and was wondering if you could explain?