Princess Diana died in a car crash in Paris in 1997 after allegedly enduring a chase by the paparazzi.
Asked whether he feels at peace with his mother's death, or whether it is "still a wound that festers", he responded: “I think probably a wound that festers.
The duke went on to add that he now feels pressure living life in the royal spotlight.
“I think being part of this family, in this role, in this job, every single time I see a camera, every single time I hear a click, every single time I see a flash it takes me straight back,” he told ITV.
“So in that respect it's the worst reminder of her life as opposed to the best.”
Cameras followed the duke and duchess on their recent royal tour of South Africa last month, where Prince Harry traced his mother’s footsteps, 22 years later.
He described the moment as “incredibly emotional” as “everything that I do reminds me of her.”
“Being here now, 22 years later, trying to finish what she started, will be incredibly emotional, but everything that I do reminds me of her,” the duke says in the documentary.
“But as I said, with the role, with the job, and the sort of pressures that come with that, I get reminded of the bad stuff, unfortunately.”
The end of the tour coincided with the release of an emotional statement addressing the couple’s treatment by certain media outlets in the British press.
The statement followed the revelation that the couple are suing The Mail On Sunday for breach of copyright and misuse of private information after the newspaper published one of Meghan’s private letters to her father, Thomas Markle.
And days later it was announced that Harry is reportedly taking legal action against two other publications over “the alleged illegal interception of voicemail messages”.
In the powerful statement, Harry wrote, "I lost my mother and now I watch my wife falling victim to the same powerful forces."
It has been an emotional week for Prince Harry. Earlier this week he attended the annual Wellchild Awards in central London with his wife Meghan. But while speaking about becoming a parent, Prince Harry teared up and had to momentarily pause his speech.
A patron of the charity which helps seriously ill children, the duke made a speech where he spoke about fatherhood.
He began: “Last year, when my wife and I attended, we knew we were expecting our first child — no one else did at the time, but we did — and I remember…”
However, in video footage of the moment, Harry can barely finish his words before choking up with tears and taking a pause.
The documentary ‘Harry & Meghan: An African Journey’, will air on ITV on Sunday, 20 October at 9pm.