Hi Florencia, If you have had unprotected sex and your periods may be late, then yes, there is a possibility that you may be pregnant. It is simply coincidence that you did not get pregnant in the past, as there is no evidence that shows a relationship between how many times semen is deposited and your chances of pregnancy. It is a little early to be feeling pregnancy symptoms, but I am concerned about the sharp lower stomach pains, which is definitely not normal. The first possibility is an ectopic pregnancy, which means that your pregnancy could have implanted outside the womb, most dangerously in the fallopian tubes. This can cause internal bleeding, and if your lower stomach pains are persistent, I would advise you to get yourself to an emergency department to rule this out. This is because ectopic pregnancies can start becoming dangerous even before a urine pregnancy test comes up positive. The other possibility is simply a urine infection causing your stomach aches, but if you haven t had any other symptoms like burning urine or needing to pee often, then this is less likely. Hope this helps, and stay safe. Please discuss proper contraception with your partner if you do not intend to get pregnant, it is too big of a decision to leave to chance. Regards, Dr. Teh