Will i get pregnant PLZ HELP ME!!!!?

ok 3 weeks ago i borrowed by best friends gym shorts n hes a guy ppl were sayin dat it might have sperm n im gonna get pregnant but im 13 and wen i wore it i had my period 2 weeks b4 then i got it 2 weeks after how long can sperm live in u without eggs er watever n im scared n dus monster kill the baby? so guys duz sperm always get on ur gym shorts n AM I GONNA GET PREG!!!!!????