03/13/2008 at 08:55 PM EDT
Minnie Driver is expecting her first child, joking her morning sickness is so bad it actually occurs "morning, noon and night."
Driver, 38, revealed her pregnancy Thursday on The Tonight Show with Jay Leno
after Leno quipped that it looked like she had gained weight from too many trips to the Hometown Buffet.
"Are you calling me fat? You've noticed my tummy, haven't you?" Driver asked.
"Are you pregnant?" Leno asked.
"Yes, I am," the actress said.
Driver said that she loves being pregnant, "more than anything else," but acknowledged, "I am sick."
"I don't know why they call it morning sickness," she said. "I am sick morning, noon and night, but it's a fair trade-off."
The British-born, Emmy-nominated actress did not say who the father was.
She dated her Good Will Hunting
costar Matt Damon
in the late 1990s, then was engaged to Josh Brolin
in 2001 and was linked last year to illusionist Criss Angel.
When her second album, Seastories
, was released last summer, she told PEOPLE
, "Much of this album is about someone who I loved very much and still have a great, wonderful friendship with even though it didn't work out."
She did not identify specifically who that inspiration might have been.