The former The Hills star admits she got "really excited" about the prospect of having a whole new face and new boobs and opted to have everything done at once.
She says, "When you have someone say, 'It's gonna be great...', then you really think it's gonna be great.
"My nose was broken so I had to get it re-done, and I was like, 'Well, while I'm there, what else?' And then I kinda wanted a few enhancements and then it got outta hand... I should have researched it more and I wasn't really told the repercussions and what would happen emotionally and physically and how much pain I'd be in."
And she also regrets a TV interview she had with U.S. news show Access Hollywood immediately after the procedures, revealing she was still "in shock" and more than a little woozy.
Speaking to Billy Bush, the presenter who grilled her about the surgery, on Thursday (18Oct12), Montag recalled, "I was kind of in shock when I talked to you... It was really kinda post-trauma; I really was kind of out of it still and recovering. I was very swollen; I probably shouldn't even have been talking at that time... I was kind of not myself."
And Montag never really got the chance to talk to the surgeon who carried out the drastic 2009 makeover to question his ethics - because he died in a horrific car accident months later.
She adds, "(I spoke to him) only briefly because unfortunately he passed away... but I was still recovering and kind of out of it, so I wasn't really in a mental place to reflect on it yet; I was still in it and still in a lot of pain."
And the busty blonde admits she should have listened to her husband Spencer Pratt, who was always against the massive makeover: "He was very against it and that was a big issue in our marriage... and I kind of just did it on my own. I probably should have talked through it with him more and listened."