I am sorry that you are experiencing these symptoms. I know it can be frustrating and downright scary when no one seems to have an answer. I am responding because I too suffer from extreme fatigue/sleepiness, neck pain, memory loss, fogginess, inability to handle stress and can't handle too much stimulus. I take Hemocyte-plus for anemia and Synthroid for hypothyroidism. I have recently been diagnosed with systemic mastocytosis. I have many other symptoms as well, so I'm not saying that this is what you probably have, but in trying to get diagnosed, I was tested by an endocrinologist first. Your endocrinologist may find some things that could lead to a proper diagnosis. When I was tested, they found I had low Vitamin D levels, which is extremely unusual for someone my age (34), & low ferratin, even though I've been treating my anemia successfully for years. I would also suggest a sleep-study test. In trying to find a diagnosis, no doctors wanted to even consider I possibly had anything else until I had the tests from the endocrinologist, the sleep study, and had seen a psychiatrist. (I have been on antidepressants for years. The doctors thought that one of the ones I was on could have been causing the fatigue. I went through 6 months of weening off one, then another until I finally got on my current prescription. Changing medications didn't help at all.) You may also want to ask about any tests for issues with your adrenal glands as that can cause fatigue as well.
I am still trying to find a solution for my fatigue. I was started on Provigil, which really helps the fatigue, but unfortunately makes my other mastocytosis symptoms worse. You may want to ask your doctor about Provigil - at least getting on it for the meantime so that you can make it through school or work, or just your day, while you continue to search for a cause and solution, may help.
I wish you the best in getting rid of the fatigue - know you are not alone.
Thank you so much for the information. I see my physician on Tuesday. I continue to pray to the Lord for healing and I will pray for you. I resent the fact that most physicians will initially assume I am just stressed or depressed. The Bible says, "weeping may endure for the night, but joy comes in the morning." I know everything will be OK. God bless you.