There is no way, no how you are pregnant. The only way is if your partner accidentally slipped into your vagina. Even if some sperm leaked onto your vagina there's no way you can get pregnant. It's too much work for the sperm to get from the outside to the inside and up to your cervix. Sperm has to be inserted into your vagina somehow.
The odds of pregnancy are incredibly tiny when having anal sex. The only possible way it could happen is if ejaculation dripped down onto/into the vagina. This is only possible because the gap isn't large. I strongly encourage you to look into birth control though, as pulling out doesn't do anything and if you do engage in vaginal intercourse you're increasing your odds greatly of pregnancy.
You might want to educate yourself on how babies are made, and until then get smart enough to be on birth control!
There is no likely chance that you are pregnant for anal sex...The only way you are going to conceive a baby is from vaginal sex, there the egg would meet the sperm...So inless you had actually had intercourse there is no possible way that you are pregnant from anal sex...and may I suggest that you become a little more informed with sex and how everything happens and birth control before continuing to have sex...
YOU CAN NOT GET PREGNANT FROM ANAL SEX... YOU NEED AN EGG TO MEET SPERM.. THERE IS NOT EGG IN YOUR BUTT