Diet and general questions

Hi everyone. I had heard from everyone that diet played a big role on the effect of uc, but I kinda ignored it in hoping it really wasn't true. I didn't wanna give up all my favorite foods quite honestly. But, I've reluctantly gone completely gluten free and mostly dairy free in hopes of getting myself out of this darn six month long flare (my first major flare). It really has helped in regards to blood/mucas, although there is still a fair point of urgency. Ive really started being cognizant of taking my vitamins and probiotics every day and I think that's factored into it too. I've finally seen some formation in my stool (which has me so happy!) Of course they are not all formed, but one or two out of the six daily is progress. But with formation comes a great deal of pain upon exit. I wanted to ask you all, what causes this pain? Is it the inflammation blocking the passage that is causing it? I've just started canasa last night, and am still on a high dose of Prednisone for the third time while waiting to start imuran.

Are rectal medications typically prescribed on a short term basis, like weeks or months at a time? Or are they usually used as maintenance drugs in addition to oral medication?