Hcg 40 at 13 DPO, should worry?

Marissa • 4th baby due 12/23/18! I have 2 girls, 9yrs & 4yrs and my rainbow baby boy, 2 yrs. 2 mc, 8/14 & 1/15.
I know I need to go back in a few days to see what the change is but I'm so nervous, I don't want to lose my third baby in a row!