Well yeah you could be pregnant....Again I ask why at 13 are you having unprotected sex?...You dont want to be pregnant at your age ...Im 18 and its hard enough for me ...School,money, job, baby....Sleep....You need to think about things ...Heck you dont even have a car ..How would you take your baby to the doctor...And how will you have money for the many things that are needed for a baby....You need to have fun while you are young and stop worrying about sex, boy, and babys....
You do need to take a hpt...But you will have to wait till 4-5 days before your next period...And tell your parents...!!!
Advice----dont have unprotected sex again...And if you are going to continue having sex be mature and tell your parents ..So they can get you on birth control...B/c I believe that if you cant tell your parents then truthfully you arent mature enough to be having sex...But best of luck!