How Can Acute Constipation With Hemiplegic Migraines Be Treated?

Hello. I normally have Hemiplegic migraines several times a month. This past week on Tuesday I used the restroom to have a bowel movement and felt a pop in the front of my head and had the most excruciating severe pounding headache i ever had. After several minutes the pain also moved down into the back of my neck. It was so different from my normal headache that I called 911 and they took me to the ER in an ambulance. The doctor did a CatScan and found nothing wrong. They gave me Benydryl and Reglan and sent me home after several hours. On Thursday it happened again with another bowel movement and I ended up at the ER again for more shots. I decided to take Phillips Milk of Magnesia to try to soften things up and move easier. It does not seem to matter, I still have the pain every time I use the rest room. I do my very best not to push and sit as upright as possible but I need to get some help for this. It is unbelieveably painful. Can you help me with this at all?