"I thought I wasn't. In passing, I said I was a little late. The doctor said, 'Is that normal?' [I said], 'No, not really typical for me,'" says Morissette, 36, who wed rapper Mario "Souleye" Treadway, 30, last May.
After the doctor took a look, he said, "This looks like the screen of a pregnant lady. And I said, 'There's still a chance that I'm not though, yes?'" Morissette goes on. "And he said, 'Yeah, about the chance that I'm getting a sex change!'"
"I was happy," says Morissette, who is five months along. "I'm glowing!"
Morissette also reveals how she was introduced to her husband.
"We met at a meditation ceremony at my house. He walked in and I thought, 'Wow, he's incredibly sexy!' but I had no idea what was to come of our little connection," she says. "He's awesome."
She's currently writing a book, but it won't touch upon her contentious split from Dave Coulier, which inspired the lyrics to her hit "You Oughta Know."
"It's a very stream-of-consciousness book: philosophy, Q&A, not a memoir... I have no desire to rehash or tell the story of my story... ever!" she jokes.
Chelsea Handler also asks if Morissette supports legalizing marijuana.
"I enjoy it sometimes, but not while I'm pregnant, obviously!" says the singer.