Period or Implantation Bleeding?

So a little back story, I did post before but I’m still concerned. Saturday, I had some light pink bleeding at work when I wiped. I put in a tampon I went to change my tampon, it was nothing on it. I thought nothing of it. Same thing happened Sunday.l, except it was dark brown & light pink at times. I’ve only had one cramp & that was Saturday. Other than that I’ve felt fine. (I’ve had indigestion at night as well for the past week.) Christmas Day, it was the same. My spotting had gotten a little heavier towards the end of the day & I wore a tampon. But it was still very light with no blood clots. Normally my period is heavy, very heavy. Today it’s red, but no blood clots.. I took a test last night It was negative. (I am on the IUD & my period was supposed to start today, but it seems to maybe have started early). Not sure what this is. Need help.