HCG Quantitative Numbers

I was seen in the ER last Friday and they did an HCG Quantitative and my numbers were 2679. something and my ultrasound showed that something was in my uterus they just couldn't definitively say what. The doctor said he was concerned because those numbers were low for me being 5 weeks. Fast forward to today's appointment with my ObGyn. He did a repeat u/s and said he still couldn't see anything but to not worry it just may be too soon and sent me for repeat lab work. Has anyone else gone through this waiting period? I'm confused and worried, just want to be able to know everything is ok so I can continue to look forward to this pregnancy.