Pain in abdominal area. Second opinion?

I have had a dull pain in my lower right abdominal area for a week now. I had visited a gastroenterologist, who checked the areas around the stomach and ruled out appendicitis. Medication of O2, nexpro, econorm, dolo 650 and zentel was prescribed. After starting the medication, I immediately noticed severe rashes appearing on the thighs, groin, and lower back region. I consulted the doctor on the same, who concluded it was the O2 causing the rashes. He prescribed Cetzin 10mg to treat the allergy. It's been close to 3 days since I have begun taking Cetzin and although the pain has reduced, the rashes are still present. Unfortunately, the lower abdominal pain hasn't fully healed either. Please suggest the next option of treatment for rashes and abdominal pain. Should I opt for a second opinion?