He's trying to hold some of it in, not just blast her with his guilt and regret but that doesn't mean it isn't leaking out around the edges. He's definitely not lying.

"I. Helped him. I wanted to believe the things he told me, I-..." Anakin shakes his head, "it doesn't matter. I was fool and I lied to myself as much as he lied to me." He doesn't meet her eyes, looking somewhere over her shoulder instead, "people think I died defending the Temple but the truth is that I was the one that led the attack."