Yes, I started feeling dizzy, lightheaded, nauseous, a little over 3 years after having it in. All the side effects (I had most)I was feeling kept getting worse over time. As soon as I had it removed in April 2007 the lightheadedness, dizziness, nausea, went away immediately and never came back. Some of the other side effects took time, and I am still getting reoccurances of them but they are lessening over time.
I had found a link months ago when I was researching this, I do not know what it is now, but it talked about the hormone levongestral (sp? which is in Mirena) in pill form caused women to become insulin resistant. Some of the side effects from being insulin resistant are the same as some of Mirena's side effects.
You may want to check into this more but give it serious consideration to getting it taken out.