Thank you for the question and thank you for visiting our site. When you are pregnant, you are more prone to bladder infections. When you have kidney stones, you are also at increased for urinary tract infections. If your left kidney started to hurt, this might be your stones acting up, but it might also be the earliest sign of a kidney infection. You need to get checked out - I would recommend that you call your OB Provider and see if they would like to see you in the clinic or whether you should go to the ER. It is not appropriate for me to make that final decision for you. I hope that this helps and good luck! Dr. Tim