brown spotting after implanon

I got my implanon out about 4 months ago. I didn't have any period for awhile and when I finally did it was really light and only lasted 3 days. Recently about 2 weeks ago I've been waiting for my next period to start but nothing. All I'm getting is this light brown spotting... it's been constantly flowing for about 2-3 weeks now. Is this still normal? It's really light that I'm only using a thin panty liner. No pain during sex or urination so I don't think it's anything like infection or worst. But just wanted to know if anyone else has had this experience.