I'm having back pain too and went to the chiropractor today. He said to try laying down and pulling my knees into my chest and rocking gently to stretch the low back. Evidently the hormones are loosening up your ligaments to allow more room for baby, which is a good thing! But sometimes that means you bones go out of place and it takes a while to adjust to that. He said women who have back pain often go on to have easier labors, because it means the body is good at loosening and being flexible (not sure if this is empirical evidence or just what he's seen in his practice, but it made me feel better!).