Help!!!! Implantation or Naw?!?!


Can someone help me to determine what this is. My periods are usually 4 days long (light, medium, heavy, light ALWAYS) April 3rd I had very very light pink spotting. April 4th started bleeding a light flow, pinkish to bright red. April 5th same thing, light flow and same color. April 6th (today) same thing. But all of my pregnancy test have come out negative and they were all quality brands. Help! Thank you!