i had the mirena in until jan this year (removed to ttc baby 4) it had been in for a year at that point and i had another one in for 18 months 6 months prior to that. for me it was the best thing as i have very heavy periods and had very little blood loss wise while it was in. i don't recall any other symptoms, but i was probably mentally just so glad at not having the ridiculous blood loss that none of that mattered. there were a couple of times whilst i had the mirena that i thought maybe i was pregnant but i think Clysta says it is one of the many side effects of the mirena that women can experience.
I had a lot of trouble with that IUD, many women have, its a terrible thing.
It's very normal actually. Mirena is a hormonal birth control and many symptoms are identical to pregnancy. I know some ladies who have had it removed for those reasons alone. They were sick of feeling pregnant all the time. You can see a clinic/doctor for a blood test just to 100% rule pregnancy out, but if it's in place and hasn't slipped, the odds would be slim.