CHICAGO (CBS) – He was thrown through the air, and slammed head first to the ground. Former Chicago Bears quarterback Jim McMahon said he always knew his body would be beaten up by playing football, but he said he did not know the extent of damage being done to his brain.

CBS 2’s Dave Savini recently traveled to Arizona to talk with McMahon about his battle with dementia, and the NFL.

McMahon has gone from high-flying fame on and the field, to a man struggling with serious body pain.

“My shoulders really are the things that bother me. I can’t sleep,” he said.

McMahon said repeated concussions during his career led to a diagnosis of early onset dementia. At times, the 53-year-old becomes confused.

“I get a little mad at myself. You know, it just seems like a simple thing, but you just can’t figure it out,” he said.

McMahon said he has even gotten lost driving home, and had to call his girlfriend.

“I called Laurie up, and I said, ‘I think aliens just picked me up and dropped me off on some other road, because I don’t know where the hell I’m at,’” he said.

Then there is the head pain.

“It felt like a knife was getting stuck in there,” he said.

Cell phone video shot by his girlfriend Laurie Navon shows him struggling with the pain during a flight.

“It’s hard. It’s scary,” she said.

She said she felt it was important to document the pain McMahon feels, because, “I want people to see what his days were like.”

McMahon said the NFL needs to come clean on what it knew during his playing days about concussion dangers, and whether there was a failure to protect players.

He pointed to other former players – including ex-teammate Dave Duerson – who suffered brain disease tied to concussions, and took their own lives.

“I can understand why they did what they did,” McMahon said. “I’m glad I’m not at that point.”

A 2009 study by the University of Michigan – paid for by the NFL – found former players had a 20 percent greater chance of suffering from dementia, Alzheimer’s disease, and other memory-related illnesses.

McMahon, who played on seven teams, said he is unable to work, and was denied disability by the NFL. That claim was for his injured body, and was filed before his dementia diagnosis.

He is re-applying, using his more recent brain scans.

“Anybody that sees those films will say, ‘Yeah, there’s something wrong with this guy,’” McMahon said.

He said he believes, overall, injuries in the league were mishandled in the past.

“At some point during my career, I had a broken neck that I was never told about,” he said. “Had I known I had a broken neck, I probably wouldn’t have been playing.”

McMahon is part of a class action lawsuit against the NFL, alleging a cover-up involving concussions and brain injuries.

CBS 2 contacted the NFL, but received no response. There was also no comment from the Chicago Bears.

Just last week, NFL officials announced independent neurological specialists should be on the sidelines next season during games, to examine and treat players for concussions. That is something the players union had been fighting for.