Can a virgin girl get pregnant with just the touch of precum on vagina. within how may days the symptoms of prgnancy occur?

Highly improbable : There has to be actual insemination for possible pregnancy. Ejaculate has to enter vagina into cervix and stay there.

Unlikely: But pre-cum can contain sperm. Thus, there is a slight chance of pregnancy if penis was in vagina. But no chance if penis did not enter vagina. Please have him wear a condom in the future if penetration is a possibility. First symptom of pregnancy is a missed menstrual period. Nausea as a symptom comes later, but certainly within first trimester (3 months)