I Have Been Feeling Faint For About Two Weeks, Usually

I have been feeling faint for about two weeks, usually starts around lunch time until two days ago. Now it starts by 9 am. Today I have been passing what seems to be a large amount of bright red blood in my stool, actually it's pretty much all blood. Can I wait for my Dr. apt on Friday or do I need to take a much quicker action such as going to the ER?