Credit: Kevin Winter/NBCUniversal/Getty Images

Megan Fox is paying for her past mistakes.

When she was 19-years-old, the actress began getting tattoos as a form of self expression. "Everyone warned me and told me, 'There's gonna be a day when you don't love this stuff anymore. You're gonna grow up,'" Fox said on The Tonight Show With Jay Leno Monday.

"I was stubborn and thought that I was going to love it forever, or that it would be like a book of my life, all the things that I loved when i was young. It's not that way at all."

Fox, who said she has "eight or nine" tattoos, is currently in the process of removing the portrait of Marilyn Monroe on her right forearm. "It hurts really bad. It's really painful. Getting them is not that bad, obviously, because I have so many."

The Friends With Kids star, 25, said that when the laser hit her skin, "it sort of exploded and looked like little kernels of popcorn popping up. It's traumatic and it's incredibly painful. They can't numb it enough to make the pain go away."

Fox, who wed Brian Austin Green, 38, in June 2010, said she's also considering erasing tattoos on her stomach and ribs. "This is going to be the least painful one to take off," she said of the Monroe tribute. "She doesn't look so good anymore!"