Education:Late period? HELP!?

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Late period? HELP!?
I am a 14 year old female about 64 inches (in height) and weight 116 and I have had my period since Sept. 12 2006 and all my periods have been regular. I recently started track and I never used to exercise before and now I have to run for an hour and a half every day. I should have gotten my period by now, but it is a few days late. I am not sexually active, but I have given and received oral sex with my boyfriend (last time was 2 weeks ago) but when he ejaculates I don%26#039;t let him near me. As far as I know, I am not expericencing any prengancy or PMS symptoms. Is the exercising effecting my hormones?? I am really scared that I might be pregnant. Thanks :]