Pregnant. Went to the doctor, now I'm VERY distressed and worried.. any advice or similar situations?

I found out I was pregnant (at a clinic yesterday with a urine test) and had six positive hpt before that. All (even the doctors one) were faint positives. The doctors estimated that I am 6 weeks. But we did an ultrasound today and couldn't see or hear anything but a tiny fluid pouch too small to even take as a real pregnancy. My boyfriend and I disagree with the whole 6 weeks thing, and think it might be closer to 2 or 3 weeks, the most it could be is 5. Is something wrong?!? I am FREAKING OUT worried sick. I want this baby to be alright and healthy. They reffered me to another doctor for bloodwork to make sure its not an ectopic pregnancy or that I am not miscarrying. Did anyone else have an earlier pregnancy than estimated and not see the baby on their first ultrasound?! I'm just looking for someone to say this happened to them and it was fine. I need some hope...