From what i can still remember he just have alot in his mind.
He still believes that Josh wants Peter's alpha parent(he doesn't know it's him).
He believes that Josh will go with the team after their contract is done.
He thinks his dangerous to be around Josh (he gets kidnapped, and this recent chapter) so he fully believes Josh won't choose to stay with him because he'll worry about Peter's safety too (this I'm not so sure is i remember it or understand correctly.
And also there's the fact that him and Josh haven't really talked after Josh got exposed that he's omega.
And so he was like if I can't have Josh or I am just going to be a burden to Josh I'll just end it all.
And i think there's also some that involved his trauma from his family.
Thought of course correct me if I'm wrong

I feel bad for Chase he's being misunderstood by the manhwa readers, since he doesn't have inner thoughts, maybe if you guys read the novel you'll feel bad for him too instead of talking bad about his actions .