Implantation bleeding?

My period is always regular, and I never have any spotting / bleeding before my period. My period is expected on this Saturday the 16th.

Over the past few days, I’ve had a few instances where when I wipe I have the tiniest bit of darkness on the toilet paper. Last night (the 12th), I was having really bad cramps (which was out of the ordinary) and was thinking maybe my period was going to start early overnight, so I put a tampon in. Took the tampon out this morning, and there was a very small amount of dark brown discharge (I say discharge because that was more like the consistency of it). I haven’t had a tampon in since, and there’s nothing there when I wipe, so I know it wasn’t my period.

Just took a pregnancy test (not on FMU, I know I’m mad at myself too) and pretty sure they are negative. In some lights I feel like I can somewhat see something, but not totally sure.

Has anyone experienced this before? Would really appreciate anyone’s input!