When to tell employers

I’m 18 in high school and found out I’m pregnant the 6th, I’m a dish washer and main thing I do is lift heavy bins full of plates. Hey also ask me to lift huge buckets ( I’m going to say no next time they ask) and also issue with using bleach and cleaners . When should I tell them, I’m not ready for people to know is there anything legal that can protect me from them telling other people