No period

So my last period was in July , the 6 th -10 th , I didn't get it in August, and still haven't gotten it, I know it's only the 6 th but I haven't had any signs of my period coming, and I have tested 3 times and all negative, I tested before my missed period, I tested on the 18 th of August and on the 27 th all negative I haven't really changed anything in my life and I'm not stressed what should I do.