No yolk sac???

I went for my first sonogram today to confirm the pregnancy, I'm at 7w1d, this is my second pregnancy, I miscarried the first one last year. Today's visit, my doctor said things aren't 100% perfect, the baby is there with a heartbeat but they can't visually see the yolk sac and sac surrounding the baby appears to have a bulge in it. He said with that, I should come back in 2 weeks for a follow-up sonogram. In the meantime I'm a having a nervous breakdown. Has anyone else experienced this or know anyone who was told the same thing. He said the pregnancy still could turn out normal but right now it's to soon to say things are 100%. In two weeks with growth of the uterus and baby, he is hoping to get a better visual.