Low HcG Level help!

Well, I got my BFP today a faint positive line on my urine test & went to the dr. to confirm & sure enough I am pregnant! However, as I was leaving she pulled me into a room & said I want you to come back in 2 days because based on your last period your HCG should be much higher, it was 15.45. According to charts online this is completely normal based upon when I think I ovulated.  I am almost certain I do not ovulate until late in my cycle, I'm thinking I'm anywhere from 7dpo or 13 dpo. I am trying to stay happy & positive but I am still very worried! Help! 😩