I don't know how big you are but a belly support belt could help if you're getting big and that's the reason your back is acting up. Also, stretching is good. You can google stretches for sciatica or lower back pain to get some ideas.
I had that too in the first trimester, it was excruciating pain. Doc said its the sciatic nerve in your back and it has went away mostly now since I'm in second trimester but also doc told me it will most likely come back when you get big and baby starts running out of room
I went.to the doc.for the same thing. My doc says its fine, as long as I dont start cramping and.bleeding.,take it easy and good luck