Working while pregnant

So I was recently promoted at work. I love my job and I love my coworkers, but I hate this job while pregnant. On Monday we had an inventory so I worked 4pm to 1am. Then they scheduled me to come back at 7 am. I then worked a 10 hour day doing a truck and pushing freight because one of my managers writes the schedule and only scheduled my team til 11, then 12. After that it was all me. I'm just exhausted and I called out today because my back and hips hurt so bad I can barely walk. I feel like my managers don't understand at all. There is a doctors note on file and I'm 31 weeks pregnant. Am I being a baby for calling out today and expecting to not have to do so much physical labor.