Is Pregnancy Possible Through Anal Sex?
Use emergency contraception.
Detailed Answer:
Hello and welcome,
Yes, you are at risk of getting pregnant, because his penis likely had semen on it, and you are at your most fertile time (approximately 2 weeks before expected period). The risk of pregnancy is not as high as if he had ejaculated in your vagina, but there still is significant risk.
I do not know what is available for emergency contraception, but I will advise according to what we have in the US:
1. The most effective form of emergency contraception is the IUD, such as Copper T, if inserted within 5 days of having had unprotected sex. This is done by a doctor. After it is inserted, it can stay in and be used as a regular contraceptive.
2. I don't know if these are sold at your drug stores (pharmacies), but hormonal emergency contraceptives are effective, but the sooner they are used, the better. They have to be used within 5 days at the latest. They can mess up your natural cycle (such as make a period come early or late) but usually only for 1-2 cycles. Emergency hormonal contraceptives are products with levonorgestrel. Here is a list of some of them, but they may have different names where you live:
http://ec.princeton.edu/questions/dose.html
Note that Plan B is only effective if you weigh less than 165 lbs (74 kg).
I hope this information helps. Please let me know if I can provide further information.
No research on a percentage available.
Detailed Answer:
There isn't a percentage available to go by. The consideration is if he had any fresh semen still on his penis that made contact with your vagina.
Yes, you should be safe now.
Detailed Answer:
Yes, it is meant to use within 72 hours. This should keep you safe.
Just so you don't worry, your period may be irregular this month because the emergency contraceptive pill is a high dose of progestin hormone. So you may have spotting, an early period, a late period, etc. But you should return to normal next month.
You may want to consider getting on a regular contraceptive so that you don't have to worry in the future.