The constant oppression of work stress made him feel suffocated.

oppression 是名词，来自动词 oppress（压迫、压制），由前缀 op-（表示"对抗"）和词根 press（压）组成，指"持续的压迫或压制状态"。在这里形容工作压力像无形的重压一样让人窒息。