No line progression

Got faint positive on 9/10 DPO PM and tested 10/11 am and pm and pm was darker. But it hasn’t gotten darker since. Any idea why the aren’t getting darker. My first pregnancy I found out same DPO; I could see the line progression each day, I miscarried at 5 weeks but I did get a dye stealer.

I’m currently 3 weeks 4 days. Is this a HCG concern.

Btw. The lines are pink. My camera is not the best at picking that up.

Top: 10/11 DPO PM

Middle: 11/12 DPO FMU

Bottom: 12/13 DPO FMU