Take a test. It's unlikely you're pregnant though with that timing, more likely you're having a long cycle.
Take a pregnancy test first and foremost..many things, stress, changes in diet, STI's, STD's, etc, can cause a late period, seeing as you're very terrified sounds to me like stress could play a big role. The first day of your period you're not fertile, a woman is generally fertile about 14 days after her period, so I highly doubt pregnancy is the problem here, however it only does take one time, so make sure you use protection for more reasons than just an unplanned pregnancy.