Generally if you don't have your period then you're not ovulating. Except for the first time you ovulate before your period returns of course. (Some people ovulate without periods but that's not the norm)
So if you catch that first egg on it's way out, chances are good! I know i am ovulating b/c i get a little pain, and my CM changes. Oh and i am definitely up for a bit more action when i'm ovulating, so that's a bit of a sign for me.