Hi, welcome to our site. I am Dr Saumya Mittal. Read your query. That is a very significant question and i appreciate your problem. I will try my best to answer your query the possibility of headache is low due to lactose intolerance. directly, they are known to cause mainly gi symptoms like abdominal pain and diarrhea and vomitting however too much of these symptoms may cause metabolic disorders and this may lead to headaches however you said you have long standing headaches. i would come to think you probably have what is called chronic migraine i would suggest you try migraine prophylaxis I hope this helps you. Inform the reports mentioned above so i can be of help further. Best of luck. I have given you the answer to the maximum considering the information provided. The results of the tests could further enhance my answer to you. Please do understand that some details could be extracted from a detailed history and examination. Looking forward to your return query with the details asked so that I can help you further. (If the answer has helped you, please indicate this)