Oh sayang, I understand how worrying this must feel for you. The good news is, quite a few mums I know had the same experience, scan at 6 weeks only showed the sac, but when they went back a few weeks later, everything was perfectly fine and baby was growing beautifully. One mum in my group mentioned she was in the exact same boat; by week 10 or 12 her little one was there with a strong heartbeat, alhamdulillah. At 6 weeks it's still very early, and sometimes the dating might be slightly different from what we think, so the sac showing up first is actually quite normal. Just make sure you're taking your vitamins, eating well, and follow up with your scan as your doctor recommends, that's really the key. Wishing you all the best, and do check in with your own doctor too, okay?