Did the doc say your boyfriend has colitis or ulcerative colitis?
Is he seeing a gastrointestinal doctor? or is it just the GP?
How long has he had it?
What symptoms is he having?
Bentyl and levsin are both antispasmodics...if he indeed has ulcerative colitis, he should be on medications to stop the inflammation by treatment, and then meds for maintenance.
What meds before has he been on? I wouldn't suggest prednisone before he's had any of the 5ASA meds...both oral and rectal.
Where in the colon is his UC.....limited or throughout?
Does your boyfriend want to be on meds....or is it that you want him to be on meds? What does he think of his lack of treatment?