Nexplanon period torture

Hey I need your help! I feel like I'm going to go crazy. So I've gotten a nexplanon which is a reversible long term birth control that's placed on the inner side of my arm. I got it on 1/20/17 everything seemed perfect until I got my period for the month of February. After the week of my expected period I continued to spot/light flow and still am. I've been bleeding for practically 4 straight weeks and in 6 days I'll be expecting my next period for the month of March..I've read the side effects and it did say that prolonged periods may happen but I didn't expect it to be an entire month! The part that's really giving me nerves is that the majority of the spot/light flow blood is dark "old blood" and no unusual scents. Should I be concerned about the dark blood? Sometimes I feel like it appears brown sometimes? What should I do?!