Dear user, welcome to healthcare magic. Although mirena implant is the most effective reversible contraception, still there is a failure rate. One in one thousand gets fregnant after one year and seven in one thousand get pregnant after five years of mirena use. There is always a chance of pregnancy even after bilateral tubal ligation. In any menstrual irregularity pregnancy must be excluded by a blood test. The symptoms you mention are non specific and non conclusive. I suggest you have a blood test for pregnancy to cut short your confusion. If the test is negative (my expectation), so consider these symptoms a temporary side effect of mirena. Good luck. Dr. Ahmed Bahaa.