Can sperm survive on a wet bathroom loofah (made of plastic) at a room temperature for 3-4 hours? if it then was used to wash a vagina (say, without soap), is there any chane of getting pregnant? thank you?

No: Pregnancy is not possible in above circumstances. Contraception remains otherwise key in avoiding undesired pregnancy and associated anxiety when intercourse becomes possible.

Agree with Dr. P: What you described has very low risk for pregnancy. Have a healthy diet, exercise 30 minutes/day, drink plenty of water daily so your urine is mostly colorless, have safe sex, no tobacco alcohol weed or street drugs. For nutrition: http://www.choosemyplate.gov/. Get HPV vaccine. Wish you good health!