weird missed af? only 17

so my period is 8 days late and I have been getting light brown spotting for 9 days now. The spotting is not heavy, it's barely enough to be on a panty liner and usually only when I wipe. since the first day of my missed period i have been really moody like I was gonna get my period. also I had small cramps. I took a pregnancy test 2 days ago in the afternoon and it was negative. has this happened to anyone?