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From you symptoms alone it sounds like chronic fatigue syndrome. This usually presents with widespread myalgia and arthralgia, headaches, chronic mental and physical exhaustion, cognitive difficulties, concentration difficulty and memory problems.
Then you also need to investigate other causes of brain fog like liver dysfunction (get liver enzymes done—liver function test), kidney dysfunction (get kidney function test done), and anemia. Multiple sclerosis is another thing that should be seriously considered. So also depression. In depression ante-depressants of all types do not help, hence you need to consult the doctor for a change in prescription to see what suits you.
Hope this helps. Do discuss this with your doctor and get yourself examined. Please let me know if there is any thing else and do keep me posted. Take care!
Brain fog can happen with multiple sclerosis, fibromyalgia, stress, lack of oxygen to the brain (perhaps a TIA or have low iron in your blood) and probably a host of other things as well. Have you had a brain scan? Have you had your blood iron and ferritin checked? It is plain from your last two sentences you are deeply depressed and in need of spiritual and professional help. If you want to know the Author of eternal hope, feel free to PM me to learn about my reason to live. If you are contemplating suicide right now and have no one with you to protect you from that, please call
9-1-1. Life is precious.