David Arquette Feeling 'Replaced' As Courteney Cox Dates New Man, Parties Away The Pain

As David Arquette tries to deal with the fallout of his recent relapse and painful breakup from his girlfriend, an insider tells RadarOnline.com that new reports of his ex-wife, Courteney Cox dating her Cougar Town co-star Brian Van Holt have sent him into a tailspin.

"Courteney was seeing Brian while she and David tried to mend things," the insider confirms. "It's giving him flashbacks."

Though David is telling friends he's happy that his ex has found love, "He's always been bad with hiding his true feelings," the source says. "Inside, it's killing him to see her with a new best friend. His status is taken over… He feels replaced."

Caught in an emotional maelstrom, his drinking "is only escalating," the source says. And rehab is not in sight.

"David needs to accept the fact that he has a problem," the source says. "He's in denial."

Just Wednesday, David was spotted out at West Hollywood hotspot The Abbey partying and celebrating the Supreme Court's ruling against DOMA and Prop 8 with his trans sister Alexis Arquette.

"David was drinking beer the whole night, a lot of it, and toasting with champagne too," an eyewitness tells Radar.

"You could tell he was really excited about the court's decision and even said it was 'awesome news,' but it was sad to see someone who was once sober drinking so much."

The source continued to describe David as being in good spirits, laughing and joking with his sister -- and dressed "like Liberace."

"While David was clearly having a great time, it was obvious he was drinking some sort of pain away," the source says.

But don't expect Courteney to stage another intervention, like she did in 2011.

"The scenario is different this time," the first source says. "One, she's not involved, and two, she's got a life that doesn't revolve around him any more. She's got a boyfriend that has his life together and can make her happy. … She doesn't want to babysit now."

"David will only go to rehab if it gets worse than it did last time," the source says.