My last period was on January 25th 2013, my period ended thursday January 31st, and on Friday (the first) I had unprotected sex, I had heard that there were very little chances of pregnancy the day after your period, but my period was due today and nothing. Im very very worried, should I be scared?
You had sex on day 7 of your cycle. Sperm can survive about 5 days.
Normally you'll ovulate between days 11 and 16 of your cycle. So, if you ovulate early there is a chance of pregnancy.
With any sexual contact there is a risk.
You can be late sometimes, for no known reason. Give it a few days. You can test now if you'd like, be sure to use your very first morning - wakeup - urine for the best accuracy.