Anyone is still working on site when you are 17 weeks pregnant?

I have been working as a technician (fix machine) for a year already and now I am 17 weeks. I am still working on site. I walk a lot, bend down, and sometimes work under hot sun. I am very tired. I want to know is it ME alone can't quit the job and have to continue work like this? Anyone work on site until you can take maternity leave?