To answer your question, I was on Zoloft for a few months to help with post-mirena symptoms. I was feeling better, so weaned myself off, and got pregnant (surprise!) a couple months later. My daughter is 1 1/2 now, and healthy. If you are planning, I would recommend waiting until you feel a little better before getting preggers though. It's nerve racking to be pregnant and not feeling well, not knowing if it's ok, or if it's because of Mirena.
Good luck!
-nile