"[Pregnancy is] horrible. Nothing is beautiful, nothing is magical. I don't care [if] you're that person who gets that pregnancy, good for you. I will remind my children every day of their lives what I did," she said.
"I was, like, hospitalized both pregnancies."
Clarkson and Blackstock married in 2013 and share 2-year-old daughter River and 5-month-old son Remy.
The singer had admitted Tuesday on "The Ellen DeGeneres Show" that she doesn't want to have more kids.
"We have four because I married into two," she said of Blackstock's two children from his previous marriage.
"I already have days where I, like, cry, so we don't need any more kids. It's a lot."
Clarkson had revealed while pregnant with Remy in November that she was getting "IVs and fluids" because of "all-day sickness."
She had similar symptoms with River, telling DeGeneres in 2013 that she was vomiting "a good dozen times a day."
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