I really cannot comment as I have had no back pain at all through 4 pregnancies and labours. I just thought that I would answer as no one else has yet!
I can understand why you are concerned, having just recently experienced a m/c with similar symptoms. All I can suggest is to see your GP or OB/GYN and ask all the questions, everybody experiences different things throughout pregnancy as I am sure you are already aware!
Best be to go to your doc and you will feel much more relieved with an expert answer/opinion
Bookmarks