My husband had his entire stomach and part of his esophagus removed due to cancer. By eating, he stretched his small intestine and it formed its own "pouch". The symptoms you describe are the same ones my husband has had since the surgery. He didn't require radiation or chemo but eating is torture...uncomfortable more than painful. The gas and poor bowell functions may stay with him forever, according to the surgeon. It's been 11 months and he has finally gained 2 pounds from his lowest weight. He has no energy, though.
My point to you is that the symptoms you describe now may be the normal dispensation of the disease and not a "relapse" as you fear. I hope I am right. Good luck to you and your family.
Wendie