I've had sex the 15 using protection n having strong pains like cramps and pain leads to lower back pain is my period coming or am i pregnant?

Hard to tell...: It can be hard to tell if a woman is pregnant because some of the symptoms seen in early pregnancy can also happen in non-pregnant women. A urine pregnancy test gives a reliable result if done correctly. One can test about 3 weeks after sex (when conception might have occurred), or 1 week after missing a period. An ob-gyn doctor can evaluate any persistent or worrisome symptoms.