urgent help pls: how can I ask for layoff, I don't want to quit

I have been working on my current job for more than 3 years now and had received good performance views every year. About 3 weeks ago, they suddenly asked me to hand over my current job responsibility and to help training someone else to do my current job. They switched me to do something very chanlenge and doesn't match with my previous work experience. It won't be reasonable and fair to force me quit the job due to their changed job responsibilities.

Due to the high pressure, I have been suffering with insomnia for many nights and rely on sleeping pills. Planning to see doctors.

I wish they lay me off, I don't want to quit. Is changing my job responsibility a solid excuse for asking lay off?  Can someone give me advices on how to argue with them?


Many thanks!