Curt Schilling revealed this morning that he has been suffering from oral cancer — the result of a 30-year chewing tobacco habit that the former Red Sox ace said he wishes he never began. “I do believe without a doubt, unquestionably, that chewing is what gave me cancer,” Schilling said during the WEEI/NESN Jimmy Fund Radio Telethon. “I wish I could go back and never dipped.” Schilling said he went through seven weeks of chemotherapy and radiation to treat squamous cell carcinoma, the cancer in the lining of his mouth. His doctor, Dr. Robert Haddad of the Dana-Farber Cancer Institute, said the pitcher’s prognosis is very good. “It could be so much worse,” Schilling said. “It could be one of my kids.” Schilling, speaking on the “Dennis & Callahan” morning show, said he kept his diagnosis under wraps for months — he was diagnosed last February — because “I didn’t want people to feel sorry for me,” and because he didn’t want to become part of the chewing tobacco debate.