Jay Cutler and Kristin Cavallari -- IT'S OVER!

Chicago Bears quarterback Jay Cutler will be about 110 pounds lighter when he enters training camp this year ... because he just dropped his fiancee, ex-MTV star Kristin Cavallari.

10 months after they began dating ... and just 3 months after they got engaged ... People.com is reporting the couple has split ... and suggest it was Jay who did the dumping.

Pretty shocking news considering they just hit Miami together earlier this month.

Don't be shocked if Kristin begins rooting for the Packers.