Low HCG

I had my HCG blood test today and the nurse told me I'm pregnant! I was so excited, but after telling me I was pregnant she mentioned that my HCG was only 44 and they thought it was a little bit on the low side 😒 I did mention to her that I have had a positive test since day 5.5 post transfer and they have gradually gotten darker and she said that is a good sign. Now I'm just in my own mind freaking out thinking maybe this pregnancy won't make it, I go back in on Friday to see if my numbers have double. Anyone start with a low HCG after a FET and everything be fine? Any input would be appreciated 😊