Implantation bleeding or early period?

Rhiannon

So I have been tracking my cycles since September 2017. My cycle ranges between 31-35 days long. Never earlier, never later. 32 seems to be the most popular. However today is CD 28 and I have some light pink spotting. When I start my period it’s normally the exact day the app predicts, maybe a day earlier, never later. I’m extremely confused. Implantation or period!? Help!