What Causes Lightheadedness, Fainting Episodes And Black Stool?

Question : Last evening, after a family dinner at a restaurant, I became light headed as we walked out. I sat on a bench waiting for the valet parking attendant to bring our car around. THings went dark, and I came to being held up by my daughter and I was sweating. I was probably dehydrated when my husband and I arrived at the restaurant and drank 1 bourbon with lots of ice and water, followed by a glass of wine. I had Bariatric surgery in 2009 and cannot eat much, stopping when I begin to feel full. My son-in-law called 911 who responded first with firefighters followed by an ambulance. The EMTs ran an EKG which was normal, so my husband and I returned home. I drank 3 glasses of water over 2 1/2 hrs before going to bed at 11:30. About 1:30 I awoke needing to urinate and intensely hungry, feeling the pressure in my esophagus in the middle of my chest. As I approached the stairs from out 2nd floor bedroom, I felt dizzy and decided I should not walk down them alone. I didn't want to awaken my husband since he had had a colonoscopy yesterday and an interrupted sleep the night before. So, I stayed in bed, sleeping fitfully until I got up at 5:30 am. I have been sipping coffee with milk and ate 1/2 a banana. I just went to the bathroom and passed a very soft almost black stool. I am supposed to fly to France Friday night to lead a training program for a major corporation next week, and I will be 65 in August. Should I be concerned enough to try to see my GP today?