IUD in arm? anyone?

Brittany
Has anyone else gotten the IUD in their arm recently? I got mine about two months ago and my last period was 2 days late and lasted 8 days. The first 3 days were light spotting and the last 5 days were regular period. This month, it is now 6 days late and hasnt even started spotting yet. My boyfriend has came in me recently and I'm a little worried that the birth control could have failed. Just wanted to see if anyone else has had this problem with their IUD? Please help!