Black blood then red?

So I haven’t had a period in about 2 months before this period. My period has become irregular and I can no longer track it because of my birth control (Nexplanon). This period is different, first off the first day the blood was black and stayed black pretty much for the last 6 days. On day 7 it’s a bright red, I thought my period was done and then I wipe and see bright red. Another thing not normal is my period is 7 days now when normally 3-5 days. Is this normal for the blood color to change at the end of period? Also was clotting a lot