How often

How many weeks or days should you take a preg test since your miss period!! 
​My last period was on aug 25, and yet haven't had any signs of getting my period! We did try getting pregnant, and I did try the ovulation test, last month! And yet I haven't gotten my period, I took a preg test couple of days before my period and it was negative and now I took another one last week but it was also neg, I'm i taking them too early? Or I'm just over thinking?