Mirena (levonorgestrel) iud for 7 months. Happily NO bleeding/spotting since insertion. 2 days ago began bleeding very heavily. Normal? Possible causes?

Unprotected sex? If you have not been in a long-term mutually monogamous relationship, both of whom are disease-free, get checked for an sexually transmitted disease. Also, an exam can detect if you have irritation of the cervix, which can sometimes bleed. Any new meds or supplements? If so, & not prescribed, stop. Can be other causes, & if no chance of std & problem happens again, get checked. If fever, pain-ER!