Mama, 4 bulan belum masanya untuk contraction macam ni, please call your doctor or go to the clinic/hospital today, okay? GBS positive pun normally they monitor je, tapi hardening + contractions + pain up to your back kena check immediately to make sure baby okay. A few of us mums pernah panic macam ni and turned out fine after doctor checked, tapi better safe than sorry, don't wait, go today. Sending you strength!