Implantation bleeding?

So Sunday I was at work and I need to pee and I look down at the toilet and there was only two small droplets of blood. Then when I wiped there was a nickel size portion a blood. And so I though I was on my period. So I put in a tampon and took it out 8 hours later and the tampon was white. Absolutely no blood at all. Well I was supposed to start me period yesterday. But no period yet. And I never ever ever spot. Could this be implantation bleeding? When is the earliest I can test?