I don't understand !?! :(

My af was due dec20th and she never showed I didn't want to take a test cause there always bfn !! :( .. so yesterday there was a bit spotting of pink (tmi) .. but it wasn't all day and then today I thought my af would show its ugly face and no she didn't so I tested and it was no surprise a bfn :( .. im so sad and confused I dont understand im 8 days late :( & still got a bfn there's only 4 days left this month so im so confused :( .. anyone??