Arm Implant and Discharge

I have the arm implant and my period went off about two weeks ago i was spotting for about 2 days but not anymore (that’s not the problem). The problem is that since i have stopped spotting i’ve been having thick dark brown discharge (for about a week now) i’m not sure is this is common on the implant. If anybody else has had this problem can you tell me if it goes away on its own or is this a concern for my doctor.