When to tell new job im pregnant

I am working 2 jobs. I am 19 weeks Tuesday and kinda showing but can hide it well. Legally i dont have to say anything till 28 weeks. Both jobs are casual. I have been with my first job for 8 months and told my boss a week or so ago and shes busy trying to think of an excuse to get rid of me, its obvious... all of a sudden she has complaints from clients and i cant help but think shes gonna be rid of me soon. Which is why im hesitant to tell my new job. Ive been at this job for a week, done 1 training shift and have just 9 hours work this week. I am thinking i need to tell them asap and i want to, but i dont wanna end up JOBLESS.