One, abnormal vaginal bleeding- It is generally a symptom of advanced cervical cancer, because it means that a tumor on the cervix is spreading to affect nearby tissue, call your gynae immediately.
Two, extremely heavy periods- this isn't about your period lasting a day longer or suddenly seeming a bit darker. Rather, it’s your period all of sudden lasting two weeks instead of four days or having two periods in one month. It's worth talking to your gynecologist.