My Name Is Earl's Jaime Pressly tells PEOPLE she's been prepping for a mommy role all of her life. "I used to rock my Cabbage Patch dolls to sleep every night when I was little," says Pressly, 29, whose son Dezi James was born May 11 in Los Angeles. "It's all I've ever wanted to do." Her fiancé DJ Eric Cubiche, 32, meanwhile, is still a dad in progress. "He never even changed a diaper before, but he's a quick learner," says Pressly, who describes Dezi as a mix of the two of them. "He has my coloring but Eric's nose and cheeks. And of course we think he's a genius." Pressly is getting as much time in now with 7-week-old Dezi as she can. She's back to the Earl set in August. "I know it's going to be hard," she says. "If I just go to the gym or the office for a couple of hours I miss him. Going to work will be tough." Meanwhile, she's savoring every minute. "We are both head over heals in love with him," she says. "We're constantly playing with him. ...He's just a joy. Smiling and easygoing. I guess that means the next will be a devil." Next one? "We hope so," says Pressly, who recalls advice Pamela Anderson gave her years ago. "She told me that if you have children you will never be lonely again," says Pressly. "And she is so right."