Hi, Doctor, I'm Nick. I'm 18 And I'm Very Worried

Hi, doctor, I'm Nick.
I'm 18 and I'm very worried about my brain mri results. The image that was taken from the top of my head or a middle horizontal slice shows that there's lots of space between my brain and the skull.. The space gap between the skull and the brain gets up to 0.83 inces from one side symmetrically. Also a possible link may be that in middle school I had long hair. To keep it in shape I used to shake my head left to right very hard. I remember having extremely painful and frequent headaches and it also affected my performance at school... The scan results showed that everything is going well overall, but I've passed an unspecified mri test and there was a very small amount of information. I think it's a possible brain volume loss.. I have heard that neurons do not regenerate ,so if my brain consists of it , it will not grow back? if it's so , will it grow back, or is it irreversible? Will it affect my life in the future?? Please help me, doctor, I can't find this information anywhere...