I had brain fog for 8.5 years and got really bad 2 -3 years ago. In my case, stress and high carbohydrate (e.g. sugar, rice, flours, alcohol) intake seem to make it worst but it was not the cause. Supplements help to reduce the inflammation but did not fix the problem. I was cured last year 2013 by my new dentist. I had a serious root canal infection in the upper jaw, nearby left nasal area. After removing the nerve, cleaned up the root canal and with 2-week of antibiotic intake, all of the sudden the brain fog completely went away. There are other brain fog causes such as Candida overgrowth, food allergies, mold infest room or contaminated air will cause brain fog, too, because I had been through this path. It is a long story. Pay close attention to your surrounding and take notes. Check out this website http://www.drlwilson.com/articles/brain_fog.htm. It is educational and helpful. Good luck and best wishes.
I felt really lost and isolated when I started new schools, but it goes away. You get used to it. I hope that's all this is.
I replied to your private message. I know about the brain fog you're describing. It does sound like possible depression to me.
Update: today in class i could not focus at all, not even write four simple sentences and was extremely distant from the people around me
Any change in your life whether it be good or bad can be very stressful.
The brain fog could be depression and anxiety. I'm sure you must have a school counselor on your campus. I recommend you talk to the counselor and tell them how you're feeling.
Moving away from home and starting college can be so stressful. I really hope once you get used to things everything will get better. It may very well be a good idea to go to school closer to home.