This may be a stupid question but my periods have always been irregular...we’ve been trying for a…

This may be a stupid question but my periods have always been irregular...we’ve been trying for a little under 2 months. I didn’t get my period a month ago when I should’ve but all tests come back negative. I’m due for another period now. If I don’t get it but the tests are still negative how would I know when I’m ovulating?