Mum-to-be Kelly Clarkson insists she is done having kids after two painful pregnancies.

The Stronger singer is in the final weeks of pregnancy with her second child with husband Brandon Blackstock, who also has two kids from a previous relationship.

And, as Kelly prepares for the birth of their baby boy, she admits this will be the last time she's going through the pregnancy process since the journey has not been an easy one for her.

"Oh, no, we are done," the pop star told Australia's KIIS FM radio station. "Oh good Lord, yes, I can't be pregnant again. This will be our number four total, so we're good... Honestly, the first one was really rough, and I was like, 'Oh, it can't happen again,' and no, it happened, like, way worse this time."

Kelly, 33, previously revealed she suffered from hyperemesis gravidarum, a condition which results in severe nausea, vomiting, weight loss and dehydration.

The singer's illness was so bad the first time around that she had to receive regular IV drips due to her extreme dehydration.

British royal Catherine, Duchess of Cambridge, suffered the same condition when she was pregnant with both her children, Prince George and Princess Charlotte, and even had to cancel a string of royal engagements due to its intensity.

"It's 100 times worse than morning sickness," Kelly added. "I just get hospitalised, and I have to get fluids. It's just, like, my body was not made to be pregnant. I wish I was like the girl that (gushes)... 'It's beautiful', but it's not."

Kelly and Brandon, who wed in 2013, welcomed daughter River Rose in 2014.