You really should use a condom with anal sex. Two reasons, if your boyfriend ever touches your vagina during anal sex you could get pregnant and second, he could get a bacterial infection.
The only thing you can do at this point is wait. Keep in mind that the stress could delay your cycle, so try not to worry. I would be willing to bet that you are not pregnant.
But I'm worrying so much abt it. My bf says nothing will happen as he thinks his semen did not come in contact with my vaginal hole. My period is supposed to start on the 8th of September.
Its not completely impossible to get pregnant from anal sex, there are documented cases, but it is highly unlikely. With all the measures you took, it is even more unlikely. Don't worry, you should be good to go.
Anal sex dosent get u pregnant the only way u could be prg is if u rubeed his semen on the outer part of ur vagina( because sperm swims) but still its un likely if his semen stayed in ur butt!! And the u pooped it out??