p.s. you can also get pregnant if you experience anal sex and he switched from anal to viginal immediately without using a condom.
You can NOT get pregnant by anal sex! It must be through vaginal intercourse and I'm assuming your are not practicing safe sex if you are concerned about leakage.
What can happen is that you can get pregnant if ovulating, since you are expecting to menstrate and having unprotected sex through vaginal intercouse. I can't stress enough how important it is to be responsible and use protection to avoid " life changing " unwanted pregnancies, transmission of STD's or with anul sex HIV. Please contact a gyne and discuss birthcontrol options for you and he must always with our without birthcontrol use a condom! Judy