Back pain 38 weeks

SF • We have a 5 yo and it took about 4 years of trying for our 2nd, due in July.

What do you do to ease your aching back? After a few hours of being out at with my 5-year-old, I end up with so much back pain that it's exhausting and so terrible. I can't get comfortable (not sitting, not standing, not laying down). The only thing so far to help has been a warm bath/shower. But I can't just stay in the bathtub for the next 2 weeks. Right??? ;)