Yes. Possible. Hindi lang naman semen per se ang nakakabuntis. Nakakabuntis din ang pre-cum.
Wait it out for another week, if hindi ka pa rin magkakaperiod, try another PT. Sometimes PT cannot detect super early pregnancy. If negative sa PT after a week of waiting and wala pa ding period, have yourself checked by your OB dahil hindi rin naman normal ang delay sa periods lalo na kung regular ka.
Gabbi