Never had children, tried the pill, the patch, and nuva ring-----all had bad reaction.

I had mirena inserted on March 20, 2012. It was very painful however, once the procedure (took ten minutes) was over the pain subsided significantly.
Now I did have very SLIGHT spotting for a couple of days but no actual bleeding until my regular period started on April 2, 2012.
I have had the WORST cramping on and off for the last 5 days and I don't know if this is normal. Usually my cramps before mirena would put me on my sofa or in the bathroom doubled over in agony for the first two days.
My doctor said the mirena would help with my pain on top of giving me lighter periods after my body adjusted to it.
I'm just worried that something is wrong with the placement or Im rejecting it, maybe it's trying to come out. The pain is not consistent it comes and goes like a contraction but when it comes it brings me to tears and it's unbearbable, but when it eases I feel completely fine until the next episode comes. Does anybody have any input or someone has maybe had this problem? I can't see my doctor until May 15 which is a month away and I don't want to overreact if it is just my body getting used to the new birth control.