According to Now magazine, friends say six months pregnant Katie, 34, is 'devastated beyond belief' by Kieran's betrayal and that it has 'left her in more pain that when Peter Andre left'.
A friend told the mag: "When she split with ex Peter Andre it was a completely different pain. Neither cheated. This is completely different because she has been betrayed in the worst way.
"Kate keeps saying this is the worst pain possible. Her head is a mess, she's feeling devastated, destroyed and hurt beyond belief."
Another friend told Closer that Katie is desperately worried about the affect her recent stress levels will be having on her unborn baby.
They explained: "Katie's trying to stay calm for her baby's sake, but she's barely eating or sleeping and is devastated.
"She's distraught and has told friends she fears for her baby's life and will blame Kieran if she loses the baby."
Katie is expecting plasterer and part-time stripper Kieran's second child - and has said she still wants him to be at the birth. She has four other children; Kieran's son, baby Jett, Peter Andre's children, Princess and Junior, and eldest son Harvey, whose father is Dwight Yorke.
More on Parentdish: Pregnant and betrayed Katie Price deserves our sympathy, not condemnation