Wishful thinking or onset of period? please help

Hey Everyone :-)
I had my implanon removed on the 10th (last monday) and since then me and my partner have been sexually active every day. My period is due the 21st but yesterday i started to get brown,pink and then it went to red discharge by the end of the day which only happened after going for a wee.
Today it has stopped completely but i have cramping in my abdomen.

Is this just the start of a period?