Low HCG Level Questions!!

I went in for my annual obgyn appointment and noted that I had a BFP Saturday. They did a test and seemed concerned that my test came back a little lite. We had blood drawn and I’ll get the results back tomorrow, but I’m so worried about the baby. Have I done something wrong? Is the baby ok? The first day of my last period was December 26th and the doctor estimated me off of that date putting me right at 6 weeks pregnant. Is it possible that I conceived half way through January instead and I’m just so newly pregnant that my levels are just not strong enough? Thanks

Update: just got off the phone with my doctor. The blood work shows my levels are only 13 and she’s extremely worried, but is questioning my time of conception as I still am not showing any signs of MC. Please pray for me guys... we’ve been trying and praying so hard for this pregnancy. I am feeling like a failure right now 😞