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He's getting so big!

Fergie went for a stroll with her baby boy Axl yesterday, and we can't believe how much he's grown since the last time we saw him!

The singer just celebrated her 39th birthday this past Thursday, and hubby Josh Duhamel presented her with a sweet cake with their son's picture on it.

Her actor husband recently revealed he snagged the Black Eyed Peas front woman by simply telling her she was hot!

"It sounds corny when you say it, but I think she knew I was sort of saying it tongue-in-cheek because she had already known that I had a little bit of a crush on her while she was there and it was sort of a way of saying something she already knew," he told E! Online.

Fergie Ferg is a lucky lady!