Credit: Steve Granitz/; Keith Allen Phillips/Splash News Online

A few months ago, Michelle McGree bragged about her alleged affair with Sandra Bullock's husband Jesse James, her ex Shane Modica tells

"She told me that she was hanging out with him and she was gonna marry him and be with him forever and all this stuff," he tells Us. "But she says that about every single guy she meets, so I don't really believe half the s---t she says."

McGee - a tattooed San Diego stripper who claims to be 24 - also claimed that Bullock, 45, and James, 40, were "breaking up," Modica says.

She used to say that "Sandra’s never around, that Jesse does whatever he wants to ... Sandra doesn’t do anything for him, all that stuff. And I told her she's an idiot," McGee says.

He tells Us he didn't know when McGeee and James "got involved ... I don't know if this was made up in her head. I can’t say if they've seen each other or not, because I don't believe anything she says, truthfully."

McGee -- who reportedly earned $30,000 for telling all to tabloid In Touch -- is upset their romance ended and that's why she's speaking out now.

"She's trying to get paid off it," Modica tells Us. "I think it’s all about money. That's her only motivation ... Money and fame. That's all she cares about."

In court papers filed last Friday, Modica asked for temporary and legal custody of their 5-year-old son Avery, whom he said was in danger in light of McGee's sex scandal (he claimed she exposed their son to pornography). A judge denied Modica's request.

Despite the request, Modica tells Us he's still "friends" with McGee. But he says: "Our son comes first."