Ex-NHL star Tim Thomas is explaining why he vanished from the public after his retirement in 2013 ... saying he's been dealing with serious brain damage from a concussion.
45-year-old Thomas -- a 2011 Stanley Cup champ and Boston Bruins legend -- got emotional with reporters before his U.S. Hockey Hall of Fame induction on Thursday ... saying his everyday life was changed after a blow he suffered in his final season.
"I woke up the next morning after it and I couldn't decide what I wanted to eat, where I wanted to go," Thomas explained.
"I couldn't plan a schedule. I survived following the team schedule the rest of the year and just made it through that season."
Thomas said his condition worsened to the point where he moved to the woods to avoid speaking with people close to him ... and didn't watch hockey because he couldn't keep up with it.
"I couldn't communicate with anybody for a few years," Thomas said.
"I didn't call my dad. I didn't talk to anybody. There was a time period where I hated the game, so to speak ... My rebound effect was like, this wasn't worth it."
Thomas says he's gotten much better recently ... thanks to recovery methods like oxygen therapy and water with ionic minerals.
Thomas said it was tough for him to speak with reporters on Thursday ... but ultimately felt it was the right thing to do and was happy to tell his story.