I've got a app now thank you but I can ovulate different times of the month as normally have a 28 day cycle But it's 24 this month so I will use opks as well
My cycles are irregular. 28-40 days. Well it's hard to say. You need to work out all the days you ovulate for every possible length of cycle you may get. Do you have a period app which has ovulation on it? Also you can go by your Cervical Mucus. It will look just like egg whites...and it should stretch a bit between your fingers... it could be streaked with white discharge also. This is fertile mucus which means you are in your fertile period and likely to ovulate. Hope this helped :)
There are free ovulation tracker apps too
If you're irregular the best thing is to get an ovulation tracker put in as many past cycles as accurately as you can and ilk give you an estimate of when you may ovulate. That's the most accurate way to figure it out without tons of fertility tests and stuff.