Question!

I have a job interview as a cashier and I am 24 weeks pregnant I don't look like it at all but am I suppose to tell them? I'm nervous they won't hire me because I'm pregnant. I also have a job interview tomorrow as a teacher assistant..what if they both want me to start I wouldn't want to turn down today's if they offered me the job would I just have to decide which one I want and call back saying I got offered a better job ?