What Causes Heavy Bleeding When On BC Pills?

Hi,



I am 34 years of age - female.

Have been taking pill for 6 years always on time.

never an issue with periods.

6 months ago started having sore uterus, cramp-like pains.

Ultrasound showed nothing.

3 weeks ago breakthough bleeding started - sore uterus, frequent urination. Bleeding got heavier and then nothing when peiord due. Now few days after period supposed to end, which never started, and breakthough bleeding started again with pains. Not pregnant, took two tests to make sure.