Frustrated

I work all day everyday I'm 35 weeks I'm due Jan 9 and I'm always at work the schedule is posted 3 weeks in advance my next day off is the 14 & after that I'm not off until Christmas then right after I'm having my baby I feel like I'm going to be so exhausted during and after birth I can't take any time to just relax and get prepared. I'm a cashier at Walmart so all I do is stand on my feet. Ughhhhh!