When should i take maternity leave

Hello ladies i am expecting twins and i am almost 13 weeks. I was just wondering what is a realistic time for me to stop working because i work at chrysler on the assembly line 10 hrs a day 6 days a week and im standing on my feet the whole time. I know im gonna get huge with this pregnancy because i already look like im 5 or 6 months prego

My doc said i should b able to carry them until im at least 37 weeks pregnant. Please help