Try calling your doctor's office one more time and stress how bad the bleeding is and how bad you feel. Be really nice, but sound weak and desperate (sometimes that works). Tell them you'll come in at any time or see another doctor in the practice.
If that doesn't work, I think you should try to see a different doctor (maybe permanently, because if you can't see your doc in an emergency, what are they good for?) or even go to an urgent care clinic or the ER if you absolutely can't get in anywhere else. With such heavy bleeding you could easily become anemic and that could be serious.