I am on the IUD and have no periods or spotting...I had a friend who recently got pregnant while on the iud...How would. You ever know?

Rare. Not having a period is common with the Mirena (levonorgestrel) iud. Failure of the iud is uncommon. If pregnancy occurs, other symptoms such as breast tenderness or nausea will be a sign.
Unlikely. Iuds are very effective, well above 99%. If you become pregnant, it is generally due to it having come out. If you did, you would have cramping, morning sickness, perhaps breast tenderness.