What Causes Black Outs With Normal Echo And Stress Tests?

Question : I have passed out recently while on an airplane. My doctor has done an echo cardiogram, heart monitor, stress test and said the test were normal. Lately, I have been getting migraine and tension headaches. I have a lot of pain in my neck and mid back. I was also told there is straightening of the cervical lordosis. Disc desiccation is noted throughout the cervical spine and decreased disc height and spondylosis at C5-6 and C6-7. The signal and caliber of the spinal cord is within normal limits.I have episodes of passing out. I have been feeling light headed every day. The doctors have done a CT scan. I have recently had a carotid and aorta ultrasound and waiting for the results. Based on this information, do you think passing out has anything to do with my heart or valves? Or, are there any other tests you would recommend that would cause me to pass out? My regular family doctor did the examination and requested these tests. One year ago, they diagnosed me with sleep apnea. I am still passing out and feeling light headed even when I use my CPAC machine at night. I have never been seen by a cardiologist. When I was a child, I passed out frequently. The doctors were not able to figure out why and said I would grow out of it. My episodes of passing out did stop for several years. However, they started again about two years ago. I would like your opinion. I feel as though I am not getting enough oxygen to my brain.Thank you.