Piper welcomed her son Winston with husband Laurence Fox in 2008.
However, in an interview with Glamour, the Secret Diary Of A Call Girl star admitted that she struggled to cope after giving birth.
"The doctor said I had post-natal depression," she explained. "Secret Diary was a stressful time. I had started leaving Winston. I was finishing breast-feeding, which was really emotional. I don't know what warrants post-natal depression."
Piper added that she refused to take any medication, saying: "They prescribed pills, but I never took them. Pills frighten me. They're a road to nowhere. I feel I'm too strong in mind and spirit for pills. I didn't feel it was that desperate - just a bad day."
Fox has also revealed that he found it difficult to deal with becoming a father.