IBS & Radiotherapy

I have had IBS for years & have managed it with a mixture of Mebevine or Buscopan & occasional loperamide. Earlier this year I was diagnosed with cancer & I have since had a hysterectomy & radiotherapy. It only took 2 sessions of radiotherapy to put my stomach in diarrhoea. Even though that finished 4 months ago I am stuck in a spiral. I have chronic diarrhea, watery no substance for up to 9 times in a short space of time. Take loperamide X2. Don't do for a couple of days. Go to toilet normally once or twice, then diarrhea starts again without warning and we start again. Doctors & hospital not being very helpful. Any idea's on what I can do different. I have changed my diet to follow BRAT as much as I can.