Tmi spotting after period

I stopped my period roughly Saturday. I bled for 7 days but it was lighter than usual but still a healthy amount. Enough to definitely be a period. Thing is it was super late. Like I didn’t even get it a month. I had a vfl on a blue dye. An obvious faint line. Then I had a negative (someone thought there was a line but I doubted it) red dye test. Then I got my period a week later. So here I am almost a week after my period stopped spotting again. Also I’m on nexplanon. Why could this be?? I used to spot a lot but I stopped spotting in between periods months ago.