Ovulating! What I need to know!

Okay so glow is just becoming very inaccurate for me. My periods are always earlier then the prediction and I’m having sex on or just before my “ovulating day” but am I? Like if my periods are wrong then maybe everything else is? So ladies how do YOU know when it’s time to get busy. Is there a way you know by your CM or mood or even some weird crazy thing that only your body does. I just need a little help understanding my body and not relying on a app.