When did you stop working?

Just a general question I’d like answered. I’m currently 28 weeks and i planned to work til I absolutely could not anymore. Lately I’ve been getting very easily irritated, the nausea is coming back, horrid lower back pain/sciatica, and so much more. This is all a problem because i work in an office setting where I sit all day and meet clients, and I’m expected to smile and provide awesome service. I’m just so tired, sleep is nonexistent and the smallest things irritate me anymore. I’m wondering when it would be acceptable to stop working.