The actor announced this year that she was stepping down as the Time Lord, after she and showrunner Chris Chibnall made a pact to do three seasons.
But Whittaker told Entertainment Weekly that once the cameras started rolling on her third and final series she was seriously tempted to stay on longer.
"There was a point where I was definitely like, 'Uhh, I don't know'," she said.
"We started this [series] and I was like, 'I don't know if I'm going to be able to commit to this decision'."
However, Whittaker said as she got stuck into filming she realised it was “the right time” for her to hand over the Tardis.
She said: “I know at some point there will be another Doctor, and I feel I can wholeheartedly give them this, through tears, and go, 'Aww, mate, you lucky f*****, you are being given an absolute pearl’.”
Whittaker – who became the first woman to play the Time Lord when she took over the part in 2017 – will leave the BBC sci-fi show next year, after starring in her third series and a set of specials.
Chibnall, who cast her in the role, will leave at the same time.
He will be back in 2023, the year the programme marks its 60th anniversary.
Watch: Jodie Whittaker to leave Doctor Who alongside showrunner Chris Chibnall