IUD Confusion :/

Megan
Ok so long story short -
I got my IUD put in 1st of Dec
I am now supposedly 20 days late with my period
I wasn't pregnant before I got the device
I don't think I'm pregnant now as I was told it would be quite painful/lots of cramps if I did while having the iud 
In saying this I have every now and then felt little "twangs" like tiny cramps but they go almost instantly 
And before I had the IUD I was having periods every other week due to stress but my stress has dropped heaps so I'm also wondering could it be that my body is just getting back to a normal cycle?
And I know the MIRENA is meant to stop periods but I have the COPPER IUD and I am still ment to get periods?
Also I can't go to the doctors hence it being Xmas and New Years. Can anyone help or has anyone been through a similar experience?