Madalas ko maranasan ang sakit ng balakang at my 33weeks. Mejo may konting sakit din sa PP pero nawawala naman at tooerable yung pain na di nag cau cause ng discomfort but when my OB checked, 1cm na pala ko which is too early kaya naconfine ako at pinakapit si Baby para umabot ng term nya. After a week sa hospital, nawala na ung pain and no sign of labor naman kaya nakalabas na ko pero 1cm pa din ako by that time. In your case 37weeks kna so baka sign na yan na malapit kna mangitlog Mie. But then of course, it may different in your case vs mine so it's always better to consult your OB.