Hi and welcome to the forum! I am glad that I can help you.
You would like to know the cause of the high temperature, diarrhea, abdominal pain and pain in the shoulders and neck that you are experiencing.
Bacterial and viral infections in individuals are characterized by increased body temperature. Depending on the organ where the inflammation reaction is, there can be additional symptoms such as a sore throat for pharyngitis, a headache for sinusitis, back pain and stiffness for meningitis and abdominal pain and diarrhea for enterocolitis (bowel infection). In certain cases, the pain and increased body temperature appear in inflammation of the appendix and the gallbladder, but the location of the pain is different.
Given the symptoms that you described, you may be experiencing an infection. Have a blood count done to rule out bacterial or viral causes of the infection. Consider seeing a specialist for infective diseases if you experience stiffness in your neck, pain all down your spinal column when moving or photo-phobia. See a gastroenterologist if you have jaundice or an abdominal surgeon if the abdominal pain is located in the lower left part of your abdomen.
Please keep in mind that I provide medical information only. I am not able to diagnose medical conditions online. Please contact your doctor or other qualified healthcare provider such as a specialist for infective diseases, gastroenterologist or abdominal surgeon for further advice and information about diagnosis and treatment options.