I want to thank you both for your answer :)
I agree with sammy73 women do not always have their menstration on the same date every month, it varies. I'm sure it will arrive within a few day. Also, you can't get pregnant thru anul sex and the chances of getting pregnant from outside dripping is slim. I do recommend that you become better informed and research, menstral cycle, reproduction cycle, consequence of unprotected sex, protection or safe sex, STD (Sexually Transmitted Diseases) and HIV. Once you become better informed, you will be able to protect yourself from unwanted pregnancies or an STD. Good luck!
Periods don't always turn up exactly on time, there can be some variation, particularly at your age. Not time to worry yet, give it a few more days.
Anal sex is very unlikely to get you pregnant, but it is just possible if some of his semen dribbled out of your anus and managed to drip into your vagina. It is also possible, but unlikely, if he had vaginal sex first (without reaching climax) before moving to anal, there can be some sperm in his pre-come.