What Causes Severe Abdominal Cramps Along With Brown Drainage From Navel?

I had a G tube put in 1 month ago because I have cancer in my throat & can not swallow. I get very bad stomach pains as if I have a torn muscle & also brownish crystals oozing out from under the button ( not a lot ). I still have stitches holding it down. Any ideas ? I start Chemo & Radiation tomorrow & I am worried about getting a pain & moving during Radiation