BBT chart

Emily • Pregnant with #3! Due May 6th 2015
I'm so confused. According to my other tracking app my avg O is on CD17 (which is today). But still no + OPK... I have a huge temp drop on the 12th BUT that night the furnace was off and our house was extremely cold so I feel like that was the cause of that drop.. Maybe I'm wrong tho? I took an OPK the evening of the 12th and there was a line but it wasn't darker than the control so it was - and it's been that way since... 
​Did I already O or maybe just not yet?