Advice needed!

Madison

My past two pregnancies one of which ended in a mmc my lines started so dark! This cycle I took my first pregnancy test at 11dpo and it was a very faint positive! I tried to wait but I caved and tested again at 12dpo and it was still positive but faint and now I've tested again today at 13 dpo and it's still a faint positive! I've also had another temp drop today. Can anyone give me advice on how long I can expect until my lines get darker or could this be a chemical?