The Northern Irishman has struggled since switching his club brand at the start of the season to Nike in a lucrative deal reported to be worth $250 million (£160 million) over 10 years.
In 12 starts on the 2013 US Tour, he has recorded just four top-10s, along with a missed cut in last month's Open.
"First and foremost, I just haven't been swinging it the best this year," McIlroy told reporters on Wednesday. "I got into a couple of bad habits with my golf swing, and it's just taken me a little bit longer to get out of them.
"Obviously when you're fighting that so much, it's hard to play the golf that I want to play, which is fluid, which is free-flowing. That's the way I play my best.
"Trying to work on my swing so much this year has not allowed me to do that, just because I've been trying to get the club in the right position to enable me to get the club in the right positions that I know I can play."
McIlroy, who had won two Major titles by the age of 23, said his confidence had been gradually eroded.
"Every time you play and you don't play well, it sort of chips away at your confidence a little bit, and it's just about building that back up," said McIlroy, whose trademark curly locks were trimmed short earlier this week.
"There have been times this year where I've really gotten down on myself and that's something that hasn't helped at all, and something that I'm trying to get better at.
"But I'm sitting here as confident as I have been all year, so I'm looking forward to getting going this week."
McIlroy, who romped to victory by a record eight shots in last year's PGA Championship at Kiawah Island, rejected the idea he was struggling for form and confidence because of his equipment change for this season.
"I think it was a valid point at the start of the year, I don't think it's a valid point now," he said. "I mean, it's nine months in.
"I'm really happy with everything that I've got in my bag, and I've had the best part of eight or nine months to play with it."
McIlroy, who claimed the order of merit on both sides of the Atlantic last year, said he tried to cope with the intense glare of the media spotlight, through good and bad, by staying inside his own bubble.
"I don't think you can really prepare for it at all," he explained. "Of course, you have success, and I win my second Major this time last year and I have a great end of the season.
"I think it's all about managing expectations, managing your own. You can't really manage anyone else's. You just have to manage your own expectations.
"I've learnt to maybe not listen as much or not read as much or not look as much. Just sort of wrap yourself in your own little world or your own little bubble. It's just something that's part of the job."
Asked if there was anything he had done over the past 12 months that he would prefer to have handled differently, McIlroy replied: "I would have definitely played more at the start of this year.
"That's one thing I regret; I didn't play enough at the start of the year. I played Abu Dhabi and took like four weeks off. I needed to get into a run of events, and that's something I should have done differently."
As for the new haircut? "I was getting a little hot under here, so it's better, it's better," smiled McIlroy. "There's still a little bit (of hair) on the top, but it's okay. Short back and sides."