Iud related

I got my IUD in October and had my first period after insertion November 11-17. I wasn’t sure if the iud would cause my periods to be heavier to stop. But I haven’t started for the month of December yet. Me and boyfriend have only had sex three times since my last period all times we used a condom. Is my period late from stress, being weird from the iud, or should I be worried about being pregnant?