Karrueche Tran -- I Dumped Chris Brown Because He's a Man Whore

Karrueche Tran didn't dump Chris Brown because of the girl he allegedly banged in rehab -- sources close to the model tell TMZ ... she dropped the hammer on their relationship because he refused to stop texting his army of jump offs.

There's been speculation that Karrueche pulled the plug when she found out he had hooked up with another girl in his facility at the beginning of March -- but we're told the break-up preceded that ... We're told Karrueche ended things after she visited Chris in rehab the month before.

Sources tell us ... Karrueche saw Chris' phone during her visit -- and it was filled with inappropriate texts from other girls. It was the last straw. We're told Karrueche was especially pissed because she'd been nothing but supportive to Chris throughout his ordeal, even going to court with him.