Skyla & 5 days late! Help?!

I was on the pill for over a year and then ran out of my prescription at the end of November. I stayed without the prescription for about a month and then in late December I got the Skyla IUD inserted.

I was supposed to start my first period after getting the IUD about 5 days ago, and my periods are usually pretty regular. I'm unsure of why Im so late but wonder if it could be the change in hormones or whether I'm actually pregnant or not.

My partner and I didn't have sex but two times while I was off birth control but we always used condoms. A little more than a week after I got the Skyla inserted, we had unprotected sex and he finished inside of me, but it was about a week before I was supposed to get my period, which still hasn't arrived. I don't think that would affect my period this early on as it usually takes about 5 weeks for the body to realize it's pregnant.

Since I have my IUD I'm afraid of being pregnant and having a high risk pregnancy, but I'm reluctant to believe I could actually be pregnant...

I'm not sure what to do, or how much longer I should wait before buying a test.. any advice or experiences would be much appreciated.