Is Pepto An Ideal Medication For Crohn's Or Ulcerative Colitis?

I have either Crohn's or Ulcerative Colitis and my doctor prescribed Pentasa... I went to pick it up and found out that it was too expensive... tried to find something else but wasn't able to because I am allergic to sulfa. So after all this mess, my doctor just tells me to take Pepto Bismol tablets. I don't understand how it went from me NEEDING this $700.00 medication down to some $5.00 pepto tabs. Will the pepto really help my problem?