Why aren’t my hcg lines getting darker?

Hi all

I had a miscarriage in April and a D&C in May at 9w2d…

My husband and I tried this cycle and I got a BFP on Saturday august 21 14dpo.

I have been taking tests all week and it seems like my lines are getting lighter. Do you think it is chemical?

I’m so worried that I got my hopes up too soon, but hoping for a miracle.

The top test and was taken 15dpo, clear blue at 16dpo, second strip at 17dpo and bottom 2 today at 18dpo.

Thoughts?? 🤞