Help!

Hey ladies, I'm so confused for this month. Just wanted to know a few opinions on what's going on with me. I had sex on my firtile days but glow had predicted that my period would show 4 days from the end of my firtile window... Well I'm late.. Figures. But thing is I thought there was atleast 6-7 days from end of firtile week to beginning of period for implantation to take place???? I did spot but so little it was unreal. It was a tiny pink spot when wiped but happened just once and that was it. On the first day of missed period I did test but I'm pretty sure that's too early for the time being of amount of days which was only 4 days from end of firtile to missed first day period.im pretty sure I'm not preg but this month was too strange for me.am I the only one to exsperience this ???