Also, since my big concussion 5 years ago and whilst having a few other smaller ones I've really been pushing myself physically and mentally.

Physically I have been excercising like crazy in that time. Probably an hour a day 5 - 6 times a week quite intensely. I also have a fairly physical job too.

Mentally I've really tried to push myself in the time. 2 weeks after the big concussion I went to uni and worked myself to the bone only to discover that I couldn't learn anywhere near as well as I did previously. I dropped out shortly after. Even after I left uni I continued to pursue intellectual improvement on my own at quite an intense level. This was quite hopeless though as my cognitive ability seemed to be a lot worse than it once was.

I tried uni again and the same thing happened.

Now I tend to avoid anything mentally challenging as I have failed so many times before.

Is it possible that I have slowed the healing process by doing this for so long since my initial big concussion?