Difficulty Concentrating, Tension In Neck And Head, Always Tired, Cold Hands

I ve been feeling like my head isnt working the same. Its like now I have to concentrate so much harder, alot of the time I cannot comprehend what my teachers ask me and I feel so dumb. I ve been having alot of tension in my neck and ontop of my head. I ve been really tired all the time - my spine feels foggy when I wake up, and my eyes always feel tired. My hands are always cold . People think its weird cause they would feel fine. My appetite is normalish. I only eat when I m hungry which is in the evening.