Very concerned about this month's cycle!

Hey ladies! Let me start off by saying I haven't had unprotected sex since my period last month, which occurred on the 19th. I have STILL not started my period for the month of September, and I'm getting really worried. I never ever miss a period, although they usually start about 2-3 days earlier or later than the last month. Its the 26th, and I'm paranoid that perhaps my last "period" was actually implantation bleeding. Should I give it until the end of the month to take a test? Any advice would be greatly appreciated! Thank you!