What Causes Vaginal Bleeding And Stomach Pain After Mirena Coil Insertion?

I had a mirena coil fitted six weeks ago. 3 weeks later I developed an endrometrial infection and was prescribed two types of antibiotic, which calmed down the pain and bleeding. About a week after I finished the antibiotics I started spotting again and now have bleeding and strong period pains. Going to the toilet is really painful - particularly bowel movements. Is this normal? How long should it normally take to get used to the coil?