I Am A 37 Year Old Female. I Am Scheduled

I am a 37 year old female. I am scheduled for a colonoscopy tomorrow morning due to having a lot of blood and mucus when I attempt a bowel movement. I followed the instruction on my prep (2 dulcolax @ 11am, 1 bottle of Magnesium Citrate @ 6pm, two more dulcolax at 8pm, and another Mag Citrate @10pm). I have barely had any type of bowel movement and my stomach is distended like I'm 5 months pregnant (I'm 5'3" and 117 lbs). Should I go to the ER? I'm worried I have a bowel obstruction. I have never had a problem with consitpation (except when I was pregnant with my kids so i do know what it feels like). I had a colonoscopy a year ago and had absolutely no problem with my prep working.