Were you also passing any amount of blood for a time before you started the prep? What is your definition of passing a lot of blood (how much is "a lot") ?
Definitely let your GI know. They typically want a clean/clear bowel to do a scope so that they get clear images of your colon but if your bleeding is intense then he may have to come up with something to try and control it prior to the scope. When you do your testing tomorrow he can hopefully go in and find the source.
Oh, and while i did not do moviprep, the mucous passing is common because when your intestines are inflamed, they produce extra amounts of mucous.
Good luck on your test! :hug: