Hi. Thanks for your query. Noted the history and understood the concerns. Your short and specific history in indicative that you are suffering from something in milk intolerance hence you have to stop milk and all milk products strictly. ALso identify the foods and beverages that instigate or enhance the problems ans stop these altogether. Also get the stool and blood tested. Back pain may be secondary to the colitis one gets or can be due to local muscle spasm and related issues. Get clinical evaluation and investigations to get a proper diagnosis and get treated accordingly.