Whoa, 10 years. Does sound like a long time to have a change like that. Check in with your doctor. When was the last time you had it replaced?
I would say you are probably not pregnant. Mirena is well known for causing periods to stop. Sometimes they stop and spotting begins later or your period comes back altogether later on. This is all very normal for Mirena. Sometimes periods stop right away with mirena and sometimes it is later on. I'd say this is all normal for your birth control choice and if you are concerned, I'd set up an appointment with your doctor to discuss. good luck