I had a lot of trouble after completing radiation. And it's so cruel because you know you made it through the treatments only to have more symptoms.
I had a lot of trouble eating after radiation and my bowels never returned back to normal. I found eating a low fat, low residue diet with lots of fluids really helped.
If the pain is really troublesome, it's worth discussing with your doctor. I did not have any relief until I had surgery (loop ileostomy). I am hoping when the ileostomy is reversed in June that I won't have the same issues.