Why am II missing my period?

Kiya • 1 Rainbow baby watching down🥺🌈

So I had a miscarriage back in January and this is how my log looks from then to now, and I just took a pregnancy test which is clearly negative, and the app saids that I should be about 6 days late, does anybody know why this could be happening?

Taken at 3 mins:

Taken right at 10 mins (there’s a line with color but faint in person but it popped up between 4-6 mins I feel like a got kinda darker but I don’t wanna get my hopes up nor my partners)