Suggest Treatment For Dizziness With Imbalance

For years I feel bit dizzy after a bowel movement and I get use to it. I eat a lots of fiber and exercise regularly. I rarely have costipation. For the past couple years and every 2 or 3 months I started to have the same feeling for 1 or 2 days. Now it is almost a month that I feel this dizziness on a daily basis with the feeling of hangover. I don t drink. This dizziness could sarts at any time of the day and will last until I go to bed. I also often feel dizzy sometime when I stand up from a seating position. I only take medecine for mild blood pressure. My CT scan came out negative and soon I will do MRI with and without contrast to the neck, head and brain. Can you please tell me what is going on?