Jessica Simpson took a seat on Oprah's couch -- and expressed her "anger" with John Mayer's decision to talk about her bedroom performance in public ... though she did admit there was one perk from all the drama.

Jessica Simpson: Click to watch
In a segment that will air on tomorrow's show, Jess told the big O how she really felt about Mayer's tell-all interview with Playboy Magazine saying, "I don't want people to know how I am in bed."

As for the perk -- Jess claims her phone hasn't stopped ringing!