Quarries About Sex. Please advice.

This is the 2nd time I'm writing it down on practo. Please understand my question. Me and my gf had out oral sex. She gave me an oral first I kissed her well and went down to lick  her genetials. Is there any possibility that my pre-cum got to her mouth and when i kissed her I could have carried it from her mouth to mine by saliva. Then I went down to lick her genetials . She has irregular periods . She missed this time. And she was a bit worried. Is there any possibility of pregnancy because I might have carried pre cum in my mouth while I kissed her is there a possibility to happen such way . I'm worried because I went to her genetials after kissing her. She kept seeing whitish smear in her underpants for 4 alternative days and now it's not there. She complained it as sexual arouses. We to confirm took urine HCG test to check it gave a negative after 2 days of missed periods second was taken after 4 days of the 1 test and it gave a negative. Please advice. Thank you Docs in advance.