Bill Romanowski Says He's Feeling Great Despite '20 Documented Concussions'

Bill Romanowski tells TMZ Sports despite the repeated head trauma he suffered during his NFL career, he's still feeling great ... although he admits he has to work at it daily.

The legendary tough guy played linebacker for four different teams in the league from 1988 to 2003 ... and he revealed to us this week he ended up with "20 documented concussions" in that timeframe.

But, he said as of now, he's showing no signs of ill effects from the brain blows -- although he did relent he's working like a dog daily to make sure things stay that way.

"I got this saying," he told us, "'Don't let the old man in, because he's knocking every day.' I work at it."

The 58-year-old says he takes "a million supplements every day" -- including products from his Lean1 nutrition line -- and he works out all the time as well.

Romo says he swims, lifts weights ... and even gets in red-light treatment therapy too.

It's all clearly important to him, especially in the wake of Brett Favre's recent Parkinson's diagnosis ... as well as his family's genetic background.

Romo told us his mom died in a battle with Alzheimer's, so he's "worried" about his future.