Help with BBT

Hi everyone. 
I'm hoping you can help me. I had a positive OPK on Clearblue Digital on Tuesday and ovulation twinges since then. My temperature when down and then up, but then went down again this morning. This is my first time charting. Does anybody know what happened? I have taken my temperature at slightly different times (around an hour or so difference) because of waking up at different time. 
Thanks for your help.