Cycle day 28 no AF symptoms

Laura • Thu, Jul 25

I'm on cycle day 28 and I'm still getting the flashing smiley on my digital opk but no signs or symptoms of af about to start??? Any ideas what's going on my <a href="https://play.google.com/store/apps/details?id=com.glow.android.eve">period app</a> says I'm late by 4 days but I do have irregular cycles