Help!

I got the skyla IUD on September 28th. I got my period September 30- October 3. I was supposed to get my period November 4th but it's two weeks late. I had unprotected sex with my BF around October 17th. I've taken two tests one 7 days after my period was late and one 10 days after and they were both negative. My period was always messed up when I was on the pill but my DR said the skyla IUD wouldn't get rid of my period. Is there a chance I'm pregnant? Has anyone else had a similar problem with the IUD