What can cause prolonged period (about 3 weeks)?

Hi everybody,
I have be taking Cerazette for 4 months now and be having bedside light irregular periods until 3 weeks ago, i started bleeding and it hasen't stopped since next. Has anyone experienced the same problem have the leaflet say taking this tablet can stop you from bleeding completely and it has in actuality had the differing effect on me?
Thank you!!
Answers:

What does an ultrasound/sonogram tell ?

Please turn to the doctor. Mother bled non-stop for 3 months before she be diagnosed with ovarian cancer. It probably isn't anything this serious, but don't have a flutter with your duration.

I found this link. Scroll just about 1/4 way down the page to contraindications. It discussions about vaginal bleeding.

Period Cramps?

This can denote you can have pollips contained by your uterus, you really want to get it checked out because if so they own to scrape them stale the walls before the become cancerous. It happen to me after I went on the BC shot. I be on my period for roughly speaking 3 months before they realize what was wrong. but the pollips craft you continuously bleed and it can seem to stop for a time or so and start again or be heavy later light. IT be weird.

And Once Again?

Stress is one thought, it can hace that effect..But, I'd telephone the Dr. that prescribed the cerazette..