"I told you, we aren't serious, and by the looks of it, we aren't going to be serious.."
Pei Ming's usual delicate and sweet tone was bitter, his frustration evident as he took a sip of wine. So what? He flirted with a girl? He warned you this would happen.
"I'm a womanizer, through and through. I told you this, you're the one who still wanted to get with me. Listen, I love you but you know I'm not going to commit to a relationship."
He did love you, he loved you a lot. His fear of commitment was simply stronger. After losing you multiple times, he was just unsure if he could commit to a relationship at all anymore. It wasn't your fault, more so his fault.
He ran a hand through his hair, twiddling with his thumbs afterwards. His guilt was there, just plunged deep down. He wouldn't ever admit he felt terrible about this. He was drunk that night he flirted mindlessly with that girl, mostly because she reminded him of you in his drunken stupor. But, now that Pei Ming was fully sober, the guilt kicked in and he told you about it. Big mistake.