Released some pre cum while urinating due to erection. made sure everything goes in the toilet pot but before cleaning the seat female used toilet to urinate. any chance of pregnancy from any residue precum on toilet seat??

Sperm are fragile. They are formed with limited energy reserves that can sustain their life only inside the moist environment of the female genitals after they are emitted. Exposure to the air/drying/all inactivate or kill sperm. A fresh, wet collection of sperm shoved inside a vagina might trigger pregnancy, but the cited action does not.

No. Pregnancy is impossible from the circumstance you described. For healthy diet: http://www.choosemyplate.gov/., exercise 30 minutes/day, drink enough water daily so your urine is mostly colorless, have safe sex, no tobacco alcohol weed or street drugs.