IUD and irregular periods

so I got my skyla IUD in January. Before that I was on Depo shot and did not get a period with either (initially). Before recently, my last real period was July 2015. Two months ago (september) I got a period, and then again in October. My boyfriend and I had sex when I was on and right after my period in October and only occasionally ever use condoms. I had some spotting after my period was over, but have no symptoms of getting a period for this month (I usually cramp and break out 2ish days before starting), and based on my last two periods, I would be a day late for this one. Is this just my body regulating or should I be worried about pregnancy?