Bfp, nonexistent bfp, stringer bfps 10 days after suspected chemical

Got a bfp but then started bleeding a few days after af was due. Assumed I had chemical. I took a test the other morning and it was so faint it was nonexistent on a Walmart cheapie. Took another this evening and this line is darker than the other... I know hcG takes a while to get to zero but why are they slightly getting stronger instead of going faint