A few times in the last week I've had sharp pains in my lower back when I move. I do a physical job so it could just be that but I've just tried to do a pregnancy Pilate's DVD and lifting my right leg I got the same pains so I gave up in case I was making something worse. I'm almost 23 weeks and just starting to get a proper bump so could this be the start of SPD or is it likely to be general achynesss?