Irregular periods. WHEN DO I OVULATE?

Yajaira

So my last period was the last week of February and I haven’t gotten it yet. I started taking birth control at age 18 to regulate my period and recently stopped last year because we’re trying to conceive. I’m 28 now and I downloaded this app to see when I ovulate but I feel like it’s so off because of my irregular period. How do I know when I actually ovulate !?!?!