I hope you are still checking for an answer to your question. The Mirena IUD has THE SAME MEDICATION in it as the depo shot does. The dr will tell you that the difference is that the hormone stays local in the uterus. However, this is simply not true. They find the hormone in breastmilk, and I've had a horrible reaction to the Mirena IUD, so obviously the medication does get into the bloodstream.
You may do fine on the Mirena, as some people who have adverse reactions to the depo do fine on it. It really just depends on your body, but please take caution. If you had a reaction to the depo, you may have one on the Mirena also. I had adverse side effects from both, but the Mirena was actually worse for me.