Nexplanon Question

I just got the implant at the end of October so I've had it for roughly 2 months going on 3 and at first my period was pretty normal before I got the implant. Well I got my period about a week early in November then after that when I thought I was "ending" I didn't and I've been bleeding like not bright red but more brown color and I haven't stopped for a month and a half now. It's kind of like spotting and not really bleeding. I'm not sure if I should call for an appointment with the doctor or just not stress to much about it. Please help.