Early faint line

Got a faint positive on Friday which was 5 days before period was due. Retested Sunday with a digital and line test, line got a little darker, and digital said yes, and then today (Monday) the line got a little lighter but the second clear blue digital said 1-2 weeks. I’ve also been using test strips which have shown the same faint line everyday since Friday. So for 4 days there’s been line progress on the strips. Any idea why the line wouldn’t be darkening ? Had a chemical in sept and am worried this will end that way too.