Sleepless nights over telling my employer!

Melissa
I'm 8 weeks pregnant. I'm scared to tell my employer I'm pregnant, I've only been with this employer 8 weeks, although worked for the NHS for 8 years. 
When I first started the job role, a couple of the women joked about not choosing me for the job through fear I would go off on maternity leave and choosing an older candidate instead!! Now I am pregnant and suffering really bad with Hyperemesis but I'm too scared to tell them, what should I do?