What should I do this month?

Caroline • Had an ectopic pregnancy resulted in loss of left tube in 2013. Now mommy of a baby boy and thinking of trying for another soon.
I have irregular cycles ranging from 28-35 days so it's always difficult for me to figure out my ovulation days. I used the clear blue digital ovulation test last month and got a smiley face on day 12 so I thought I was having a 28 day cycle this month and was very happy when I was "late" on day 30. I didn't keep testing after the smiley face since that's what the direction from the test says. I took a pregnancy test and got a BFN and sure enough got my period on day 32.
​So was the ovulation test right? How come my period came so late if I ovulated so long ago? Is it possible that I actually ovulated later and got a false positive with the digital test?
​What do you guys think? Should I continue to use the test this month? And should I continue to test even after I get a positive just in case I ovulate later?
​Thank you!