他在和别人抵死缠绵
[tā zài hé bié rén dĭ sĭ chán mián]
'He is passionately entangled with another person'. While literally depicting intimate behavior, it metaphorically refers to being intensely engaged in activities or new relationships. There’s implication that something current or recent occupies much attention/effort which differs greatly from before (potentially referring back nostalgically).