First of all, I should tell you my chart is probably not all that accurate because of the thermometer I've been using. I have since bought a more accurate one, but I decided to keep using the old one this cycle just for the sake of catching a pattern. Secondly, when I first started charting, I took my temperatures at different times and also missed a few days. There is also one discarded temp from a few days ago when I temped 15 minutes after I got up (forgot again

). Now on to the point!
I was hoping some of you might be able to help with some questions I have regarding my chart:
1.
Why Monday and not Sunday? I heard that the temp spike occurs right after O, and my temp on Sunday was dramatically higher than on Saturday. Also, I checked out some other charts on the site, and I saw that the pattern of lowest temp followed by temp spike was common. In these charts, the day of the spike seemed to be when FF detected O for those women.
2.
Does the negative OPK on Monday offer any clues as to when O took place? I know the negative result indicates that the surge has already taken place, but does it mean that O had likely already taken place as well? Or could it still have occurred at anytime throughout the day on Monday? I wonder about this, of course, because I'm trying my best to determine our chances since our closest BD was on Saturday.
3.
What are my chances looking like? I know it's ideal to BD the day before & the day of O, but what do you think? Could we have been close enough? Has anyone had a pattern like this and ended up with their BFP? I'm really looking for some hope (hence the over-analyzing), but more than that I want realistic expectations! So I'd love to hear what you ladies think.
This is my first time charting, and I didn't realize O had probably occurred until today when the cross-hairs appeared. Sometimes my cycles are long, so I was expecting it to occur later in my cycle. I guess I learned some valuable lessons this time!
Anyway, thanks in advance for any interpretation assistance!