Didnt have no reason to question paternity but the day we had and the due date doesnt match up?

January 7, 2005 I had with an old friend of mine. I was out of town for the next three weeks and I tried to call her and she never answered my calls or called me back. So, I then forgot about it. On Feb 3 she calls me and tells me she is pregnant and that she is due Oct 12. I really didnt think to question the paternity until her best friend told me during those three weeks she didnt answer my calls she was staying with one of her ex boyfriends. Now, as the the child has gotten older I really am not seeing the resemblance. Correct me if I am wrong but the days seem to be off.