help?

so i work at a hole in the wall resturaunt and im constantly having to strain myself and pick up heavy things. ive told my boss i want a baby (not necessarily that i am ttc) and i guess she just didnt think of it that way. so i still am straining myself every day damn near. im scared if i tell her im trying to have a baby i will be laid off or fired. thats what my last job did and i didnt even do strenuous work there, i want to keep my job but i need to be careful so i dont miscarry in case i am to get pregnant. i know there are laws against things like this but we all know there are loopholes that they can get through. what should i do?