Faint lines; low HCG. Help!!

FGM • TTC #2 at 42. Wishing everyone sticky and healthy baby dust!
So I'm 13 DPO and got my BFP confirmed Friday. FR HPT lines were still light but the blood test says I'm pregnant. Yay!
Problem is my HCG count is 11. I'm freaking out.
Doc wants me to go Tuesday for new HCG blood test (and keep taking the progesterone suppositories).
I'm 41. Has anyone started out with such low numbers and ended up with full term healthy baby?