Dean McDermott says sex with Tori Spelling "wasn't fantastic"

Dean McDermott and Tori Spelling get candid in a clip from the new Lifetime docu-drama, "True Tori."

McDermott, 47, opens up about their sex life, saying in an April 9 therapy session that there have been "ebbs and flows in the sex department," adding, "We would have sex once every two weeks. It wasn't fantastic."

"Dean, your expectations of what a marriage is supposed to be sexually, it's like a fairy tale," the therapist chimes in.

Spelling, 40, tearfully responds, "I can never give him enough sex. He's never going to be happy with just me."

"I'm insatiable," explains McDermott, who did a rehab stint this year. "Sex was an escape, just like drugs and alcohol."

Spelling then brings up McDermott's recent affair with a 28-year-old woman named Emily Goodhand, asking: "Why her?" McDermott points out that he wasn't attracted to the other woman -- she was just "a warm body."

The former "Beverly Hills, 90210" star and McDermott have been married for seven years and have four kids together: Liam, 7, Stella, 5, Hattie, 2, and Finn, 20 months.

News of a McDermott's affair broke earlier this year.

Lifetime's "True Tori" premieres Tuesday at 10 p.m. ET. Watch the preview clip below: