Suggest Treatment For Tingling Sensation In The Brain

I think I might have a problem with my brain. I doubt that this is supposed to happen when I am changing at 15. I use to be able to have a quick response, a sharp mind, and a great memory. Since this April, and then on, my response has gotten more slower, my mind, has become duller, and when I try and figure out, or solve something, my brain just feels like as if it is always in neutral, instead of immediately looking for a solution, or tried to remember something. I even get sometimes, a throbbing, or a little pain at one point of my head, and get random high strength "tingling", in my brain, lasting a second or two. These things have never happened to me before. I am not in any stress, and I have 100% of oxygen in my brain. It just feels like if I something is taking away part of my brain, everyday. What is it, and how do I get rid of this, and try to gain back my sharp mind?