Many women suffer some form of back pain with pregnancy. Pregnancy forces the body to adapt quickly to a lot of new weight distributed on the abdomen. This can put a lot of stress on the muscles, tendons, and ligaments of your back. It can even shift the alignment of the spine.
You need to take the weight off your spine. Lying down with your back in good alignment can help relieve the pain. It is best to lie on your side. Use pillows to keep your head and neck aligned so that your spine is straight. A pillow between your knees can help. Don't lie on your stomach or back. Lying on your back puts pressure on major blood vessels, which can cause dizziness and even nausea.
If your pregnancy has changed your posture, a support harness might help. The harness helps support the abdomen, taking some of the pressure off your lower back.
Make sure you tell your doctor about your back pain. In rare cases, back pain during pregnancy can be a signal of a condition that you need to address.