Missing Periods on Implanon?

Jillian
Ok, so a few months ago I got implanon. For the first month or two I had my regular period plus some light spotting, but since my last one in early September, I haven't had one. Is this a normal reaction to Implanon, or should I see my OBGYN? There's no way I could be pregnant, as I haven't had sex since early August.