When Should I Say Something Or Stop My Job?

I’m a manager of an auto parts warehouse, working 10 hours a day, and at least half or up to 7 (not consecutive) hours of the day, I could be lifting things that are 15-30 lbs for maybe only 3 minutes at a time. It’s not all day that I’m lifting heavy things, as some things are small or light, or can be placed on a cart for easy mobility. I just found out I’m pregnant, and just wanted some advice, suggestions or opinions on when should i notify my job to see if assistance can be implemented or if I needed to stop lifting things ASAP. Because I’m so early, I’m not sure if it affects anything now, but I wouldn’t want to take a chance.