"I feel so lucky and happy and proud to be with him," the 52-year-old says. “It’s a beautiful love story that we got a second chance.”
Lopez, and Affleck, 49, rekindled their love last spring. The A-list couple dated from 2002 until they called off their engagement in 2004.
During their split, Lopez welcomed 13-year-old twins Max and Emme with ex-husband Marc Anthony, and Affleck became father to Violet, 16, Seraphina, 13, and 9-year-old Samuel, whom he shares with ex-wife Jennifer Garner.
Today, Lopez credits their time apart and life experiences to making the relationship work. "It's beautiful the way it feels very different than it was years ago...There's more of an appreciation and a celebration for it, which is nice," the "Love Don’t Cost a Thing" singer says.
“When you find somebody and you really, really love them and you get a second chance at that? That is a really rare, precious, beautiful thing and we don't take it for granted," she adds.
Lopez also notes that Affleck has done the work to be the best partner he can be. "I'm so proud of the him, I'm so proud of the man he's become that I've watched from afar,” she says. “Being honest with each other, being loving, that's just the basis of everything.”
She continues, "I feel like he's at a place in his life where — just like how I feel about myself — it's been a journey of learning yourself and figuring yourself out, getting to a place where you feel really good on your own and who you are so you can be in a happy, healthy relationship."
“They are madly in love and Jen totally has Ben's back, which is why she wanted to make her support and stance known publicly,” the source told ET.
“Things between their children are pretty organic at this point. The families respect each other and also get along, so things are all good and fine on that front," the source added. "Their friends think they will get engaged eventually and it's only a matter of time."