I Have Had On Going Stomach Problems. I Go From

I have had on going stomach problems. I go from diahrea several days to painful bloated constipation sometimes over a week. I've taken meds for ibs for over a year. Not helpful. I'm scheduled for colonoscopy but almost 2 months out. I've taken castor oil and still can't go. How long can someone go without a bowl movement? Should i go to emergency room or just wait for my scheduled colonoscopy ? My doctor otherwise has done blood work everything is fine...except very low vitamin d. I'm at a loss. In constant pain!