Needed Reassurance

I had my first doctors appointment today. It was supposed to be a day filled with nothing but happiness. Based on my last period I'm supposed to be 7 weeks. They did the ultrasound and there was no baby. Just the sac. I couldn't help but cry when there was no baby. I was so excited to hear a heartbeat and imagine my heart break when there was no baby. My doctor said I could just be too early and that the date may be wrong. She said the sac measured at 4-5 weeks. They drew blood and I'll be back on Monday for another blood draw to see if my hormone levels are going up. They scheduled me for another ultrasound in 2 weeks. I did some research and I found a lot of women who said this happened to them and they went to carry full term and healthy babies. I hope that's my case. This would be my second baby but I don't think I would be okay if I lose this child. Has this ever happened to any of you ladies out there? I'd love some advice.