YOU DO NOT HAVE BRAIN DAMAGE!! You are scaring yourself into believing that you do. Try to relax friend and think about it logically. As others have said, it is mathematically impossible to just "get brain damage". My friend, I am guilty of over thinking the littlest things as well. Every palpitation, every single little pain in my chest I am CONVINCED that I am having a heart attack. In reality I am just having panic symptoms. Go to your doctor and make sure, it will also make you feel better to hear that you are perfectly fine.
Just remember, breathe and think positive. Positive thinking goes a LONG way. Peace and Prosperity Friend.