The 'Horrible Bosses' actress - who split from her Hollywood hunk husband in 2005 -told pals she has fallen head-over-heels with the actor since they started dating earlier this year and none of her relationships in the past six years have come close.
A source said: "Jen hasn't felt this way about anyone since Brad.
"They are moving quickly, but they know the feelings they have about [each other] are different from past romances."
Jennifer, 42 recently sold her Beverly Hills mansion and she and 39-year-old Justin have reportedly begun looking at a number of homes to replace it.
Late last month, the couple - who are currently enjoying a romantic vacation in Hawaii -were viewing up to six a day, including Ellen Degeneres and Portia De Rossi's house and friends say they have even discussed marriage and children.
The source added to Us Weekly magazine: "They have talked at length about getting married and starting a family. She is anxious for the next phase of her life and feels like this is the time."