Don’t want to tell my supervisor yet

So I work in the apparel clothing department at Walmart. Very easy job. But sometimes they make us pull heavy pallets for different areas and lift heavy boxes. I don’t want to tell them just yet that I’m pregnant but I’m not suppose to lift heavy things and those pallets are stacked with merchandise including glass etc. especially I the first trimester I don’t want to overdo it. Should I just tell her if she tries to make me pull some? She’s such an evil person I’m sorry.. but it’s not only that I think she will just blurt it out bc she feels as if she can.. she’s that type of person. Idk what to do