Lower Abdominal Burning And Twitching. Anxiety, Loss Of Appetite, Constipation. Cancer Chances?

Hello. I am female 65. For decades I have had low abdominal burning in the same place and often think it is a bladder infection but it never is. It often feels like it is moving/twitching and it burns. I had a bad bout of it recently witn no appetite and lots of anxiety and ended up in the hosptial with constipation. My md is setting up a colonoscopy and gave me some ativan and celexia. He says the pain and constipation are signs of colon cancer but I have had this recurring burning in the same place for as long as I can remember. He also said I was about as anxious and dry mouthed as a person can be and gave me a shot of valium. I had been on zoloft for years but was really feeling great, no bowel issues and had gone off zoloft about 10 days before this incident happened and I thought I had sufficiently weaned over several months. I am still constipated but the anxiety is less and I have a little appetite. At the hospital they did a digital x-ray and said I was hideously constipated and sent me home with a go-easy and 3 ativan. That worked well but the symptoms returned, especially the anxiety/butterflies so I started up the zoloft at 50m day but it didn't seem to help and Dr. Wade switched me to celexia yeterday along with an antibiotic for a sinus infection. All bloodwork is normal.
My question is does colon cancer grow in the same place ibs/diverticular is and cause worse distress? I did get a diagnosis of diverticular years ago but I don't know where it is. The burning pain is in the same place it always has been for as long as I can remember and the condition has always been non-smell gas and slow moving bowls/constipation but this has been a long spell of it, about a month now from when I stopped taking zoloft, the trip to the ER with anxiety and constipation about 10 days after stopping the zoloft and now 3 weeks back to zoloft but still not eating, moving bowels much and mountains of anxiety. Then seeing Dr. Wade yesterday.