His pride man. His pride gets in the way
Both his pride and his previous experience with that guy whom he was going out with, but who treated him like a fuck toy, and then left with some other man, breaking Alex's heart. Alex is unconsciously afraid that the story might repeat with DG.
Alex is conflicted now. "Should I go for DG, or should I stay away?". That's why he just can't say DG straight in the face that he likes him, because it would be an obvious confrontation that he's so scared of. So he decides to not take a direct approach, but rather manipulate DG into having sex with him ("make-up sex") etc. It probably makes him feel safe, and there's also this possible "benefit": DG staying with him. But as we all could clearly see in this chapter, DG isn't willing to act according to Alex's plan. That's why this story is so fucking interesting.
Alex seems so desperate now, lmao. But it looks like he's slowly realising he's fallen for DG.
"I just said that to see how he'd react."
"He said what he wanted to and just left. As if he doesn't like me anymore. In some ways, that was the Dong-Gyun I always wanted. So why...?"
"He's totally rejecting me."
I'm telling you, give it a few chapters and you'll have Alex on his knees begging DG to be with him.