Faint lines and bbt drop

Last Thursday at 10 dpo I got a faint positive.
I've been getting faint positives since then, using dollarstore tests.
This morning I used a first response and I still have a faint line.
I know a lines a line, but I was suppose to get my period on Saturday and it's now Tuesday.. Shouldn't the line be getting darker? Also I had a huge bbt drop this morning before I took the test so now I'm super worried ...
Any insights?