Need a little medical advice..?

Maybe it's just a complication from the Mirena? Or possibly, and I'm just taking a stab in the dark here becuse your rash symptom goes along with it, but TSS maybe? TSS rash symptoms resemble a sunburn. Do you have a fever as well? Or you could have a bladder infection of some sort. Go visit a doctor and check it out and they can help you with the pain.