I also have the Mirena IUD. I have had it a little over 2 years now. My periods are very light like yours. All I ever buy anymore are pantiliners. I have not experienced the heavy bleeding part yet though. I too cannot feel my strings....even asked my hubby to check for me and he thinks he feels them but not quite sure. One thing I get that neither you or the other response mentioned is bad cramping sometimes. I often wonder if my IUD is not there anymore either. I haven't had any pregnancy scares thus far either. I have seriously considered having it removed but just like you I am without health insurance and fear I couldn't afford monthly birth control. The only reason I got the IUD was because it's cheaper for me and I don't have to remember if I took my pill. That part is really nice. Sometimes my breasts feels sore and rather huge as well.
I know this is of no help to you at all. All I can suggest is maybe calling a doctor and ask questions. I totally understand not being able to just rush off and see them.
Okay I know I sent you a private message in regards to Patti M's message but I can't help myself. Condoms?? Are you kidding me? Having no period or a very light one is indeed a plus to most women with an IUD but getting the IUD can also be done for other reasons as well. Like I privately told K., the day I married my hubby was the day I said BYE BYE to condoms. Those thing's are simply dreadful in my opinion and if there are other options of birth control than I would much rather go with those than CONDOMS......:)