Is there a line progression?

Heidi • Proud mummy of two beautiful boys, Isaac (01/01/16) and Jensen (14/04/18)

I've been obsessively testing since 9 dpo as I had a miscarriage last month where my lines never got darker. Does anyone see any progression between these three tests? Taken 15 dpo (pm), 17 dpo (fmu) and 19 dpo (3rd mu). Just need some reassurance. I know I should stop testing (used my last one up!).