Baby might be sitting on your nerve... Just watch some stretches you can do or join a prenatal yoga class. My back has hurt almost constantly durning pregnancy and yoga has helped so much.
Yeah I'm 34 weeks still working which is soon to cease my lower back has been killing me I went and got a snoogle boy has it been a lifesaver !!!!!
At 32w i was sitting on my floor and twisted wrong, had to have my SO get off to take me to ER. Sounds like sciatica, this late in your pregnancy your back muscles are loosening up to prep for birth so they're more susceptible to issues. For me I'm still having back pain from it., son is only 2w though. Heating pad and tylenol will help so much!