Why are my BFP’s fading?

Kelcie

Wednesday I took the first test and has a faint positive so I immediately took a digital and it said yes. I’ve continued to take them everyday to see if my lines were darkening and today (top test) it’s very faint. Has this ever happened to anyone and it ended up being okay? I’m guessing I’m anywhere from 4w5d-5w’s and no bleeding but small cramps.