My boyfriend and I had protected sex on Thursday night & found out that the condom broke. My period isn't due until the 27th. But on Friday night I noticed a tiny clot when I went to use the bathroom. Then a few hours later there was a bit more blood. But not enough to make me think my period was starting. Around midnight I went to change the tampon & there was barely any blood. Normally my periods are super heavy but I'm worried that this might mean I'm pregnant. What is implantation bleeding?