Back pain

I'm supposed to start my period tomorrow and I have been having the worst lower back pain today. I'm cramping a lot today which is fairly normal. Yesterday I had almost no cramping but still some back pain. Day before was about the same as today. Is this normal? My periods are pretty regular but I don't remember my back hurting me so much. I did have sex around my fertile time. Which was the 1st-6th. Had unprotected sex the 5th but he did not cum inside of me. Could this be a pregnancy symptom? What are my chances of even getting pregnant then? Any advice about easing the back pain. I've taken some ibphrophen but doesn't seem to help much. Tia