There is no reason to "freak out" about your period being late, or early, for that matter. Some people always have regular periods. Some people always have irregular periods. Some people have regular periods for a stretch, and then have irregular periods, and so on. None of this is reason for concern, and as specialmom said, masturbation has no relationship to the timing of your period. Hormones control the timing of our periods.
You sound quite young, and you might benefit from talking to your mom or another trusted female adult about your "freaking out" when your period is late. It really isn't healthy to focus so much attention on the timing of a monthly function (unless it relates to pregnancy, of course).
Any change in routine can interfere with your period. And all of a sudden having sexual urges might be indicative of a shift in hormones. Many women report that throughout there cycle, their libido shifts as it relates to hormones. And you could also be late because of the shifting hormones.