Hay, back pain ganyan is so common sa last weeks ng pregnancy, mama, a few of us felt the same thing and it turned out to be just the baby's position and all that weight pulling down, hindi pa necessarily cervix opening. The only way talaga to know kung may changes na sa cervix is kung mag-check ang doctor, so I'd really suggest calling your OB or going in for a checkup para ma-ease your mind, lalo na approaching na ang EDD mo! Fingers crossed na malapit na talaga ang labor, but hindi pwedeng ma-guess lang based sa pain, hopefully you're one of the lucky ones na sudden lang mag-go into labor. Strength, mama!