Implant and periods

Georgia
Hey girls! 
I have had the implant in my arm for nearly a year and a half- and love it! I get regular monthly periods, it's just some months (like this month) I get random dark brown discharge it's like a period but not if that makes sense. But the discharge has really stringy parts through it. It's gross to explain but I think it could be my uterus lining shedding? Just wondering if anyone else had this as it seems quite excessive sometimes! Thanks x