Time To Grow Up! Jason Sudeikis Ditches Party Boy Ways For Pregnant Fiancée Olivia Wilde

Mom-to-be Olivia Wilde isn't due until May, but life has already changed significantly for her and baby daddy Jason Sudeikis.

RadarOnline.com has exclusively learned that the former Saturday Night Live star and staple of the NYC nightlife scene has ditched his party boy past and transformed into a clean-living expectant dad worthy of his gorgeous and talented fiancée.

"Olivia is obsessively anti-drug, and Jason has had to leave behind a lot of his old party pals and drinking buddies since he's been with her," a source revealed to RadarOnline.com. "This is a pretty sensitive issue for her. Several of her friends say she's never got over a bad situation with an ex-boyfriend who was secretly mixed up in drugs."

Now, the source says, "Olivia and Jason live an extremely clean life and try to get away from their respective past demons in the process. They're going to make great parents."

In fact, even before Wilde became pregnant, she and Jason "were major diet and workout obsessives," according to the source, "to the point that on days they were not working, they stuck to a strict, gluten-free diet of no more than 1,300 calories."

"Determined to have a healthy baby, they have prepared extremely well for parenthood," the source explains.

Wilde, 29, and the Horrible Bosses comedian, 38, got engaged in January 2013, as RadarOnline.com has reported.

She revealed to Ryan Seacrest at the Golden Globes this January that she and Sudeikis are expecting a boy.