What Causes Irregular Menstrual Periods After Mirena Coil Insertion?

I am 42 years old, have health problems. I am diabetic and high blood pressure. I'm on tablets. In June last year I am equipped with the Mirena coil, and since then I have more back pain and become irritable. Period did not in order. every 3 or 4 month period and I have a little bleeding. Before 2 weeks the doctor has shown that hemoglobin has increased. Is it possible that the hemoglobin is increased by the issue of the monthly period? What are you recommend?

Thank you