Sounds like you have been through a lot! Your situation is extremely complex and challenging, beyond the scope of this forum, and probably even pushing the limits of a typical 15 min appointment with a gastroenterologist. Between your numerous allergies to medications and contraindications to diagnostic tests, there are so many wrenches thrown into this problem. My advice would be to seek further evaluation at an academic medical center more equipped to deal with cases such as yours. Hopefully, you can find a gastroenterologist who is patient, understanding, and accommodating. Good luck!
Do you have IBS (irritable bowel syndrome), IBD (inflammatory bowel disease, such as Crohn's or ulcerative colitis), or both? I noticed you stated you had Crohn's disease in one of your old posts. If that is the case, you already have a diagnosis for your digestive symptoms, and you should follow up with your gastroenterologist to optimize your medication regimen.
Regarding capsule endoscopy, I would not rule it out so quickly. Ask your gastroenterologist if you are a candidate. If you cannot get conventional colonoscopy, capsule endoscopy is better than nothing.
The most common applications for capsule endoscopy include evaluation for (1) obscure GI bleeding, both overt and occult, including iron deficiency anemia; (2) suspected Crohn’s disease; (3) surveillance in patients with polyposis syndromes; (4) suspected small intestine tumors; and (5) suspected or refractory malabsorptive syndromes (e.g., celiac disease).
The relative contraindications include patients (1) with known or suspected GI obstruction, strictures, or fistulas based on the clinical picture or preprocedure testing, (2) with cardiac pacemakers or other implanted electromedical devices, (3) with swallowing disorders, and (4) who are pregnant.
Source: American Society of Gastrointestinal Endoscopy Technology Status Evaluation Report, available at:
https://www.asge.org/docs/default-source/importfiles/assets/0/73730/c4d44578-c3d0-4583-9949-b15f3e8537e0.pdf
You can still consider MRI enterography. For intravenous contrast, MRI uses gadolinium contrast whereas CT uses iodinated contrast; there is no cross-reactivity between different classes of contrast media.* For oral contrast, this uses VoLumen (barium sulfate suspension), which rarely has allergic reaction.
While you should not have a contrast study if you had prior severe allergic reaction (e.g., anaphylaxis), you can still consider having a contrast study if you had prior mild to moderate allergic reaction (e.g., itching or hives), as your doctor can provide a premedication regimen consisting of prednisone and diphenhydramine to decrease your risk of allergic reaction.
If you decline CT or MRI with contrast, doing a CT abdomen/pelvis without contrast may still be of benefit. You may see obvious bowel wall thickening suggestive of enteritis and/or colitis.
*Source: American College of Radiology Manual on Contrast Media, available at:
https://www.acr.org/-/media/ACR/Files/Clinical-Resources/Contrast_Media.pdf
You should still see a GI doctor for further workup and evaluation. Even if you decline conventional colonoscopy, you may benefit from capsule endoscopy and/or virtual colonoscopy, noting the latter would still require the dreaded prep. Alternatively, consider CT or MRI enterography to rule out enteritis, colitis, or other pathology.