Pls help

So my last period was July 14 and on my <a href="https://play.google.com/store/apps/details?id=com.glow.android">glow app</a> it said I was supposed to start August 16 and I didn't so I deleted the date and now it says I start August 20 I feel like I'm not gonna start at all can u guys help me or tell me if I'm pregnant I haven't bought a test cus I don't want anyone to know yet if I am what should I do