IBS/IBD sufferers: Removing Dulcolax from 2 day prep and just doing Miralax?

I had a colonoscopy years ago and they were able to do it with just Miralax and it was fine. Dulcolax makes me pretty sick but it's on the instructions this time

This is also my first 2 day prep. I've never had the extra long prep before. I think it's because I brought up occasional constipation but I've been having diarrhea for 4 days anyways

I'm 3 days away and wondering if I can just get away with Miralax or maybe one Dulcolax if absolutely necessary. I'm supposed to start tomorrow afternoon (Wednesday; it's a late appointment on Friday)

I started the liquid diet a day early (3 days in advance, yes I will be starving) to hopefully make it easier. Should I just start a bit of Miralax now and get the train rolling?

He prescribed me the generic for bentyl to see if I am having strong gut contractions and to ease that, so it baffles me they want me to suffer through Dulcolax which causes the contractions

I'm well aware of failed colonoscopies, but I think I have time to still get clean and clear with 3 days to go with just Miralax