Question about the Implant

I’ve been on the implant for not quite two years? A year and 3/4? And for most of that time I haven’t had periods. Two cycles ago, though, I started having periods again. Now I’m late for the third! It’s my first implant and I love it, but I’m not sure what I should be expecting. Why did my period start back? Should I be worried about it being irregular? Has anyone else had things happen to their periods on the implant? I’m not supposed to need a new one till ‘19.