Understanding ovulation

Hello I am having trouble to determine whether I'm ovulating or not. AF is like clockwork, but my predicted OV dates differ from what my body is doing! I have an app on my phone called Period Tracker and my period always comes on the date predicted, but on my OV date, my body is as normal. If that makes sense! Usually a week after AF has started (lasts for 4 days), I start to get a slight cramp on one side (usually the left), it feels like trapped wind. Then, and I apologise for TMI overload, I get the wet, sticky stuff (you know what I mean!), like egg whites. Again, apologies for TMI!! From what I've looked up, this means I'm fertile. I do the old baby dancing with the fianc??, but never fall pregnant. What's up with that!? Any advice?