Very important IUD question


I got a copper IUD on 12th of December 2016

I got my period the next day normally my cycle is 28 days I haven't got my period so far keeps being pushed back oh and I had my 1st baby on October 2, 2016 could any of this affect my period this dramatic ? Could I be pregnant ? I understand there is a 1% of women who can get pregnant on the IUD

Yes I am sexual active don't know if I should take pregnancy test or not