Is Spotting Between Periods While On Mirena A Cause For Concern?

Hi Doctor, I have a mirena inserted over a year now. I have not gone back to my specialist to check it. the menstrual blood is now at a good flow...a lot less. now after my periods of 3days..its finishes. Then I get spots of blood comes back another week..its soo frustrating and annoying. its affecting my sex life too. What can be done ? do I have a problem ?