That definitely seems like quite a bit of blood to me, especially if it is that consistent. I bleed heavily for 2 days when I'm on my period, so bleeding like you described would probably freak me out a bit.
If you can wait until someone calls, wait it out a few more hours and see if someone calls. Depending what you are comfortable with, call back in a few and leave another message for a nurse or anybody to call you back. As much as I hate ER's, if someone doesn't call you back within a reasonable amount of time, I would probably bite the bullet and go on it.
Keep us posted.