I faced this same dilema last weekend, I've been flairing for about 6 weeks, I had an appointment to see the specialist, but not till the end of the month. I was in a lot of pain, looing lots of blood, and like you feeling very weak. I'd had to take some time off work because I was feeling so sick.
Faced with the option of putting up with it till my appointment or braving the emergency room and the perceived perils that lay in wait for me, I sensibly opted to go to the emergency room ....
It was without doubt the best thing I could have done, I went on Monday lunchtime (after the weekend rush) I was being seen by a Dr in 1.5 hours, the staff were fantastic, very understanding, I had blood & stool tests, saw my specialist, they took abdomial x-rays, and I came back the next day for a colonoscopy.
Now my initial appointment is my follow up appointment, I'm on new meds and symptoms are already under control. At the end of the day, it's your body and your health .. you need to take control of the situation and get the help you need. Do it sooner rather than later.