nexplanon

I didnt bleed on the shot but my "period" was longer now i have the implant & iv had my period but ive been having dark old blood come out (about the amount of a quarter or two in a whole day) ever since friday or Saturday. When will this end? It's going to be 2 weeks saturday that i have started my "period" but almost a week that this dark old blood has gone on & this is fucking long to me since i havent had a real period since October 12th. Iv been on the implant a month & havent had sex in 2 weeks because of this