could I be miscarrying?

I've heard of women having miscarriages while on Nexplanon. Me and my fiancé have unprotected sex because we are comfortable enough with my birth control. We were told we needed no extra protection with it so we don't use any. Well it's been a few weeks since the last time we had sex and suddenly I am spotting. Not enough to show up on a pad very badly but enough to see it when I wipe. Could this be a miscarriage? I don't have any pregnancy tests laying around :/