Ovulation test help.

Hi. 

To start I have really irregular periods and most likely don't ovulate everymonth. I've been waiting for what I thought was my period. been getting belly and back aches.

It didn't arrive so took a ovulation test just to see what it would say. It was pretty close to a positive (I think) so then took a clearblue ovulation test but they were empty circles. Could it still look positive if I ovulated yesterday and the day before when I was getting the aches?