Mark Wahlberg & Rhea Durham: Expecting #3!

With two toddlers already keeping him busy, Mark Wahlberg and his longtime girlfriend, Rhea Durham, are adding another celebrity baby to the mix!

Amazingly, that may be just the beginning.

"When the kids are good, we want eight or nine," Wahlberg said Monday in L.A. while promoting his new film, The Happening.

"When they're bad, we [want] to stop at three."

The couple also have a daughter, Ella (pictured below), 4 and a son Michael, 2, and Wahlberg says having a full house is "awesome."

"Hectic at times," he admits. "But a lot of fun."

In The Happening, Wahlberg plays a science teacher in the new thriller, out June 13, trying to stay alive against a mysterious and deadly phenomenon.

But the actor says his own fears are far more real.

"My fear is failing as a father, as a friend, as a son. I have a lot of responsibility and a lot of people counting on me," he says.

"And I know God has put me in this position to put back and try to create some opportunities for some others, show kids there is another way."