If i've had sex with more than 13 girls without protection, is it possible that i have aids by now?

Unprotected sex: Yes it is not only possible, but depending on your sexual partners it is probable that you have been exposed to the HIV virus that causes aids. If you have been infected then you are capable of passing the virus to your sexual contacts. See your doctor immediately to be checked. Meanwhile you should not have unprotected sex.

Maybe: Aids is a disease that you get after you have been HIV positive for a while with a CD4 count below 400. But you maybe HIV positive if you had unprotected sex with someone who has aids or is HIV positive. The best course of action right now would be to see your doctor, and stop all unprotected sexual activity.

Unprotected Sex: Having unprotected sex puts you, your partner, and your future partners, at risk for multiple sexually transmitted infections (sti), including HIV (the virus that causes aids). While some sti's have symptoms, others do not. You should see a physician and be tested for HIV and other stis (gonorrhea, chlamydia, syphilis, herpes, etc). Sex with barrier protection (ie a condom) is always advisable.

Yes: If you have sex even once without protection it is possible that you have contracted any one of a number of sexually transmitted diseases. You could also be a father now and just not know it yet. Protection is inexpensive and easily available, so why would you take those chances.