hi, i need help!

me and my boyfriend were together on 2 oct 12. (19 days past LMP).didn't have penetration neither he cum around my vagina there could be cum on his fingers he touched my vagina with. still a virgin. but i still didn't have my periods since 13 oct 12.

i've done with almost 5 hpts all are negative as i am at 8 weeks from LMP and i had ultrasound on 7week there was no gestational sac even.i've no pregnancy symptom till.

could i be pregnant??? i didnt have my periods since...