MATTHEW McCONAUGHEY stared down the barrel of a tough love gun from long time GF Camila Alves after she slapped him with a tough ultimatum: “Marry me or NO more kids!”

The “Lincoln Lawyer” star, 42 – one of three boys with a large extended family – has been begging the 28-year-old Brazilian model to add to their modest brood of two, insiders say.

But the brunette beauty – who has given birth to son Levi, 3, and daughter Vida, 2, since the couple began dating in 2007 – refused to agree until he popped the question, sources say.

That happened Christmas Day, insiders say, and now the genetically blessed twosome plan to wed in the spring and hope to announce a pregnancy soon after.

“Camila loves Matthew and wants more children with him, but marriage is important to her,” a friend divulged.

“Matthew didn’t realize how serious she was about a wedding until she made it clear that she was not having more children until he proposed.”

The handsome Texan – who’s dated actresses Patricia Arquette, Ashley Judd, Sandra Bullock and Penelope Cruz – has instructed Camila to choose a date and location, and he’ll make her dream wedding come true, added the source.

“They’re planning a beach wedding in the spring and hoping to get pregnant on or before their honey­moon,” the friend noted.

“Camila would be happy with just one more baby, but Matthew is dead-set on having a large family. He’s sure that the engagement will convince her to have at least two more children over the next five years.”