Any UK mum's having issues with work?

I've have been off for two weeks for suspected pre term labour....went back this week and have a fit note stating not to do the job I was doing and that I need lighter duties. Manager is very uncaring and won't agree to the Dr's advice! She's trying to force my maternity leave even tho I'm only 30 weeks pregnant and she can't do that. So stressed I wish I stayed off sick