Hi, I had diarrhea n vomiting 3 days ago due to food poisoning. Every time I went to the toilet to throw up or pass motion, the headache will come on...it's like a hard pounding headache. I sweat as well n cannot open my eyes. I thought something in my head was going to burst. Pain level on 1-10 would be 10! Ended up in A&E. They said it might be due to severe dehydration. Put me on drips and gave me pain meds which helped but slight dull pounding persisted. Reduced to headaches I get coz of my sinus inflammation. Meds included paracetamol wif codeine, diclofenac sod, prochlorperazine maleate and oral rehydration salts. 3 days later, again whilst passing motion the pounding headache came back. Motion was normal. Took the meds which helped but feeling worn out and really sick to the stomach from all the meds. Would like to know if these headaches are pressure related, due to dehydration or migraine? Appreciate your advice.