Chronic diarrhea can have many different causes. One of the most common is irritable bowel syndrome, or IBS, but there is no test for IBS, so the diagnosis is usually based on excluding other possible causes of chronic diarrhea. A Gastroenterologist would usually know the additional testing that would be appropriate, but the primary testing after a colonoscopy would be a series of blood and stool tests. It is also possible to have chronic diarrhea from a variety of food sensitivities, such as gluten sensitivity or lactose intolerance. The blood and stool tests can look for many of these food sensitivities, but it also may be necessary to try an elimination diet to see if the symptoms improve.
For the shortness of breath, the other primary test that would be the next step would be a spirometry, which measures movement of air in and out of the lungs.
For the neck pain, the first step would be a physical examination, but that would require you to complain of the neck pain to your doctor. Depending on the findings on exam, it may be necessary to get x-rays of the neck or advanced imaging, such as an MRI.
None of the pictures look worrisome. These are minor variation of skin and benign lesions of skin, none of which look worrisome. If there is a more prominent white coating of the tongue at times, it may be necessary to examine it under a microscope. Your primary care physician can do a more detailed skin exam than can be done via pictures, but if there is any question, the next step would be consultation with a Dermatologist.
Lastly, many of these symptoms can be related to anxiety, but that also would require that other possible causes are excluded, because there is no test that can prove that non-specific symptoms are due to anxiety.
Is there any other information that would be helpful?