First response test question

I've been taking the curved first response pregnancy tests since 6 days ago. I took 4 of them 2 days ago and they were all the same lightness. Like super light compared to what they had been. I had a tiny light brown on my toilet paper at the same time. I had a miscarriage back in January and I seriously thought I was miscarrying at this point. I'm still confused. So so confused . I'm 16 dpi today and I got this picture. In my mind I feel like I'm still going to miscarry I've already told everyone because of how light my tests were getting. I was so devastated. I also take clinical guard tests and they were lighter that night as well. Idk what's going on . I was not expecting to see it this dark.