Can this be a sign?! 😣

With my first son I tested 5 days early, strong line. With baby O I did not test positive until 5 days late, and the lines were still kind of faint around 4 and a half weeks. Currently 5 weeks! 
I'm afraid because I've read a lot of posts saying low hcg levels can be a sign of miscarriage? So nervous and my doctor doesn't see me until 8 weeks.