I'm 36+6!! And since Friday have been having period cramps on and off I seen my midwife who told me it's fine to go into labour now so if they get painful to call the hospital. But they never did get painful Just a dull achy period cramp. But this morning I sat on the sofa and got a pain in my back! Almost like I had moved the wrong way and twisted a nerve or something! Now my lower back is aching and has been for a good hour. Can you pull a muscle just by sitting down? Or am I Gearing up for the big day?