Ovulation Test

I took a test today but it’s negative again. When am I suppose to actually ovulate? Do you ever know for sure when your suppose too? How do you even know for sure?

I was on the depo before for 4 years almost 5 years (the whole time I didn’t have a period). I got off of it about a year ago, got my period 5-6 months after I got off the depo.

My period are 4 days long but 19-21 days apart.

Check marks on the non bloody days, are test results for LH surge - all negative. More negatives since December. 🤦🏻‍♀️