My girlfriend gave me oral. I touched my penis then touched her underwear, where her vagina is. Can pre-ejaculate be on my fingers and penetrate?

No. From what you described, your girlfriend is very, very, unlikely to get pregnant. For good health - Have a diet rich in fresh vegetables, fruits, whole grains, milk and milk products, nuts, beans, legumes, lentils and small amounts of lean meats. Avoid saturated fats. Exercise at least 150 minutes/week and increase the intensity of exercise gradually. Do not use tobacco, alcohol, weed or street drugs in any form. Practice safe sex.