I had sex with a girl only once without a condom on October 15, 2010, haven't had sex with her ever again. Is that the day she conceived?

I moved your thread to Pregnancy & New Motherhood, because it seemed a more appropriate board than Adult Sexuality.

Your question needs more information to be able to give you accurate advice.

How old are both of you? It will determine just how involved the answersd you receive are.

How far along is the pregnancy? Has she had the child?

How often did/do you have sex with or without use of birth control? Condoms and other forms of birth control are not 100% effective. Several of us on this site have gotten pregnant when we were using birth control.

Have you invested in a paternity test yet?

Chances are that is not when she conceived IF she is pregnant.

You see, it takes several days for the sperm to travel up the vaginal canal all the way to the fallopian tubes where the sperm meets the egg. So she could have conceived anytime during the week following your intimate encounter.