"If I knew what I was f***ing doing, I'd have already f***ing done it."
Tom Brady is fed up with everyone asking if he's going to retire ... 'cause the legendary quarterback just unloaded on his "Let's Go!" SiriusXM podcast cohost Jim Gray for trying to get an update on his decision.
The awkward moment went down as the two discussed the remaining teams in the NFL playoffs on Monday ... when Gray switched topics to Brady's future.
"Tom, you're leaving everybody guessing," Gray said. "You said you'll take your time. Do you have any type of a timetable as to what you might want to do regarding your football career?"
That's when Brady hurled his expletive-filled response ... clearly annoyed with having to discuss the topic.
"I'm taking it a day a time," Brady added.
Gray explained why he even brought it up ... explaining it's the question everyone wants to know the answer to.
Brady calmed down enough to give a bit of a laugh ... replying, "You're scratching."
"I appreciate you asking. Thank you."
The two decided to move on to other football-related topics ... including the tripping fine Brady was given for a play with Dallas Cowboys safety Malik Hooker, which he plans to appeal.
Also worth noting -- Gray asked Brady if he's picked up a football since getting eliminated from the playoffs after losing in the Wild Card round ... and his response is pretty interesting.