implantation bleeding

so i was supposed to start my period on May 3rd i had some dark spotting now its the 5th and still the same spotting and no flow. . im not sure if my period like hey im running a little late but ill be there or its hey were baking something in here so start saving your money cause its gonna be expensive. so how long is implantation bleeding?

i was pregnant last year and had no signs of it. i misscarried it was hard thing to go through. so i dont wanna get my hopes up. i took a test and it was negative but my period always flows through on the 1st day of spotting .