If you haven't had sex, I wouldn't worry about being pregnant. Your finger, or anybody else's, can't do that. If you've been doing that a lot, its possible it can delay your period, or you may have abnormal periods. I've had abnormal periods since I started when I was 11. I'm 31 now. They are never predictable and its hell.
lol, fingering can't get you pregnant.(: periods are bipolar. they won't always come "on time"