Stomach discomfort after a bowel movement

Hi - has anyone had anything like this?  I had it last year and eventually it went away.  Now it's back and they believe it's either diverticulitis or IBS.  IBS appears to be a "catch-all" phrase for undiagnosable problems.  I'm on Bentyl morning and night and the discomfort usually dissapates a few hours after my morning consititution.  Still, I wish it would go away entirely. I just wondered if anyone has ever had anything like this.  It feels like a dull ache and gets better as the day goes on.  Thanks!