Hello Dear ... Thanks for your query. First of all I want to say that if your doctor has confirmed it to be Irritable bowel syndrome after all clinical examinations and investigations then be sure that it is a functional bowel disorder.Actually there are many hypotheses about why it occurs.. You are having IBS with alternating stool pattern [ IBS-A or pain predominant ]... Your Increased gut motion with change of environmental temperature may be due to sympathetic cholinergic stimulation ... Some investigations should be done to rule out other conditions -- 1] Abdominal ultrasound (to exclude gallstones , other biliary tract diseases and other pathologies) 2] Stool microscopy and culture (to exclude infectious conditions) 3] Blood tests: Full blood examination, LFT, ESR, serological testing for coeliac disease 4] Endoscopy and biopsies (to exclude peptic ulcer disease, coeliac disease, inflammatory bowel disease, malignancies) 5] Hydrogen breath testing (to exclude fructose and lactose malabsorption) To get relief from your symptoms --- Reduce stress and anxiety,do yoga and regular exercises..You can have cognitive behavioural therapy from a psychiatrist, it helps in irritable bowel syndrome.Probiotics often help. You need to treat if any bowel infections are present.High fibre diet is recommended.Take lactose free diet if lactose intolerance is present.Selective serotonin receptor Inhibitors [SSRI] like Fluoxetine are helpful in Irritable bowel Syndrome. Stay under yearly checkup of a gastroenterologist. Take care.