Sexual Openion. Please clarify my doubt.

Me and my gf had oral sex before a month and very a pretty sure it was just an oral. She was a bit worried after that, she always has irregular periods last periods was on march 3 and this month it got skipped, she is worried and doubting about the oral we had. She kept finding whitish smear in her underpants. We checked a urine HCG test after 2 days of missed periods and It gave a negative and 4 days the next and it showed a negative to make sure. Is it normal getting those whitish smear. She told she had it before because of sexual arouses. Now she is fine and now there are no smears. She had the smear for 5 alternative days she complained it as sexual arouses. Please clarify are there any chances of pregnancy. Are there any possibility that saliva can make way for a pregnancy. As she gave me an oral, I kissed her and went down to her.it was just oral please clarify my doubt.