Jennifer Garner is finally ready to say "I do" with boyfriend John Miller , and the proof is she's openly wearing an engagement ring, but sources say it's plunged ex-hubby Ben Affleck into a deep funk, RadarOnline.com can reveal.

Sources said the 53-year-old Batman hunk never believed the 53-year-old Elektra beauty – mom of his kids, Violet, 19, Fin, 16, and Sam, 13 – would remarry and this is his worst nightmare. Article continues below advertisement

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"For Ben, it's torture," said a source. "He was clinging to the hope she'd have second thoughts and call it off, but now that's clearly not happening.

"He has to get his head

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