Can you conceive if your sperm has entered 3 days after ovulation and your ovulation period was over by that time? and can sperm go through clothes and swim up the pant leg to the vagina?

Sperm cannot go through clothes and up your pant leg. Pregnancy is known to have occurred from sex on any and all days of the cycle. If you do not wish to be pregnant, use contraception all the time, every time. You may consider implanted contraceptive, or IUD. Practice safe sex : https://www.hopkinsmedicine.org/health/wellness-and-prevention/safer-sex-guidelines