I don't understand.

I had a positive ovulation test to confirm the 25yh was same color the 26th was darker than the control line. My temps aren't adding up.. This is my 3rd month bbt charting. The first month showed the steady 3 temp rise.. The other 2 were not so clear. I temp every morning when I wake up before I get out of bed. The only thing I can think is we left the windows open to sleep and it got cold in our house. Anyone else having a problem with the charts? I just want a BFP :(