Raquel Leviss kept the drama flowing after the "Vanderpump Rules" reunion finale, admitting Tom Sandoval covered up the worst details of their hookups ... the ones that happened right under Ariana Madix's nose.

Raquel did a one-on-one chat with a 'VPR' producer for a debrief 6 days after the reunion taping, and exposed the fact she and Sandoval had actually slept together multiple times during Scheana Shay's wedding last August in Mexico. Tom had claimed it was just a "one-night stand," so ... yeah, there's that.

She even talked about suggesting to Tom they become a throuple -- Tom, Ariana, and Raquel -- which he quickly said Ariana would NOT be into doing. That's super interesting because Bravo shot a scene during the wedding trip -- which it didn't air until after the affair came out -- showing all 3 of them half-naked in a hot tub and Ariana saying, "We look like a throuple."

She had no idea Raquel and Tom were already banging.

Perhaps the most shocking revelation came when Raquel tearfully admitted bedding Tom at the home he still shares with Ariana. During the reunion, Tom was adamant they never hooked up while Ariana was out of town, attending her grandmother's funeral -- but Raquel says that's exactly what happened.

She added that particular hookup was the one Tom begged her to keep under wraps.

As she sobbed, Raquel said Tom wanted to hold on to that lie, because ... "It’s a really bad look to hook up with someone’s boyfriend in their own house" while Ariana was away at the funeral.

And there's, perhaps, the biggest understatement of the whole damn 'Scandoval.'

As for why she finally came clean, Raquel said, "I just hate lying so much."