Severe lower back ache at 21weeks

[kylieb77]

Does anyone have any suggestions to help me relieve my back ache? I feel it in the muscles around the very base of my back and top of butt. It is really bad when lying down at night especially, but I can feel it most of the time when sitting or walking. I am keeping my fingers crossed that it doesn't stay like this for the next 20 weeks or I will scream!!! Would love to hear of any effective stretches, exercises, good sleeping positions etc that may help.

Thanks x