Implantation or strange period ?

My period is due in 3 days but I have been having some really light spotting (like I wipe and there’s nothing there but if I stick toilet paper up there, there a little mucus pink and brown). It’s been happened since late Tuesday night. So we are 4 days in now . Light cramping but nothing like my period . Took a pregnancy test and it was negative . I’m at a loss .

The last time I had this type of spotting I was pregnant with my first born. Anyone experience anything like this ?