Hcg 40 at 13 DPO, should worry?

Marissa • I have 2 girls, 12& 7 and my rainbow baby boys 5 and 2. 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!