I had a concussion about 2 months ago in a skiing accident where I also broke my shoulder. Everything is all healed up these days, but I was out of work for about 5 weeks.
I'll report my broken shoulder when I get my new medical in the fall, but there is no way I'm reporting the concussion. I'm 23, in great shape, never had a concussion before, and my head scans came back fine, but after talking to several people, they advised against reporting the concussion due to stories like yours. One of the stories came from a captain that I recently flew with. I guess he had a buddy that had a concussion where everything was fine with the CT scans and all, but when he reported it to the FAA same thing happened to him. His medical was pulled right away. He said it has been over a year and he still hasn't gotten it back.
That story is why that captain didn't report his past concussions either, and he has had 2 of them. Both were from skiing accidents when he was a skiing instructor where people ran into him and knocked him out.
Sorry to hear about your head injury, but it seems you're going to have a long uphill battle on this one.