I just had sex for the first time a few days ago and my period is a week early. is that normal?

Yes: for several reasons. First, fairly young, menstrual periods vary more. Second, the local stimulation might change hormonal levels. Third, spotting usually occurs after first intercourse and is NOT a period.

Kind off: if you have sex for the first time ,you will end up with a period of bleeding that might not be your period. so it is kind of normal. make sure you practice a safe sex, you are too young for sex related problems and diseases. so it is kind of normal. and your period might still come in time.