I'm Unable To Sleep For 3-4 Days Continuously. On 5

I'm unable to sleep for 3-4 days continuously. On 5 th day out of sheer tiredness sleep a little. At times affected with episode lasting few hours, in which I feel drowsy, walk in zig zag manner. If somebody questions me I murmur, which can be understandable if heard properly. The next day whatever had previous day is totally forgotten. In the last 1year about 6-7 such episodes occurred. My CT scan &MRI scan are normal. Doctor suspects partial complex seizure or alzeimure. I'm 45 years old healthy male.
What can be the reason?