Jessica Simpson is finally opening up about John Mayer's raunchy Playboy mag comments.

"I don't want people to know how I am in bed!" Simpson, 29, laments in an episode of The Oprah Winfrey Show to air Wednesday.

See a clip of Jessica talking about John on Oprah

Mayer likened his ex girlfriend -- whom he split from in 2007 after about a year of dating -- to "crack cocaine" and "sexual napalm" in the March issue of the lad mag. He later apologized for being "an a--hole."

See Jessica and John in happier times

Simpson also admitted she struggles with criticism of her weight.

"It's a really hard thing for me to talk about," the clearly upset reality star (her show, The Price of Beauty, debuts March 15 on VH1) tells Oprah.

See how Jess' body transformed last year

"You were a size 4 and people were calling you fat?" the talk show host, 56, says in disbelief, referring to infamous mom jeans Simpson wore to a chili cook off in January 2009. usmagazine