Energy changes symptoms and conditions

I just had mirena inserted about a week ago....i don't have any kids and was told it's easier and less painful if you've had kids....the first day was horrible....nearly fainted after they put it in,had horrible cramping, over the next few days the cramps continued...i have prescription pain killers for cramps that did not work....still getting cramps and now, i am extremely extremely tired. It doesn't say that mirena causes tiredness....has anyone else experienced this tiredness...i fall asleep at the snap of a finger...