Spotting/early period with implanon

I've had the implanon for 2 and a bit years now, it's due to come up to the 3 year mark in October. The last period I had was just after it was inserted. Today, there has been some darkish brown bloody discharge, and I'm slightly concerned about my implant failing. It's probably more like spotting than a period (I've never had spotting before, with or without hormonal contraception involved). Similarly, I'm worried in case the implant failed and I've now done a complete cycle without realising. I'm basically just worried about everything, not to mention it's a bank holiday tomorrow, and all the doctors etc will be closed.