Hi, I understand that you use gracial daily and use condom during every act of sexual contact. With this double protection, the chance of pregnancy is negligible. Also you have not had sex since your last period. So the chance of being pregnant is zero. The low back pain may be due to other causes like a ureteric stone, or muscle spasm. Please do not be scared. If the pain has gone away, I do not think there is a need to worry. If the pain persists, take a simple pain killer like acetaminophene and drink plenty of water. If it does not help then you need to see a doctor for the pain. I personally feel that you need not worry as it does not seem to be a serious issue. Hope I was able to help you, thanks for using health care magic. Dr. Madhuri Bagde Consultant Obstetrician and Gynecologist