I used this brand before for 7 months. I have never seen three lines. The instruction do say to ignore the lines and just go by the circle or smiley though, but 3 line seems weird and I would call the help line. Both lines do go dark when I get the positive. I tested twice a day with FMU and at 7pm. My surge always happened on the evening test and was also still positive with the next morning FMU and then negative that evening. My RE office say to test with FMU. I only tested twice a day because I did not want to miss it as we were doing IUI based on +OPK, not trigger. I also pee'd in a cup and used the dip method, because I had some error messages with using urine flow (maybe too much?)
Good luck. I hope you figure out and have not yet surged, might just be a late O cycle.
p.s. I hate OPK's...they are expensive and it is soooo hard to hold your pee for 4 hours...another reason to use FMU, so much easier. I would try the twice a day method to see if you can catch the positive with FMU, then you will know approximately how long your surge lasts and if you can continue with FMU on subsequent cycles.