HMMM, I can't remember when you start taking your temp (at the beginning or end of AF). I thought I had read that you don't need to take it during AF but some do just because it helps them to be consitent and do it every day. But don't quote me on that one! I use an FM monitor because charting made me a little crazy

. After my first AF following my first m/c I took my temp every morning and my chart never showed that I Od (even though I got a positive OPK)!! I was told that sometimes your body gets reved up, but you don't O because your body is still trying to get back to normal. Plus not all women O every month.
Some people use the online charting sites which will help you identify when you O. Some even have little tutorials that teach you about charting. You should notice a jump in your temp after you O and that temp should stay up and then fall before AF shows. If it stays up when AF is supposed to show, then that is an indicator you could be pregnant.
Also, charting only tells you that you have already O'd. If you don't BD (don't know the exactly what it stands for but basically it is sex

) you will miss your window to get pregnant. I used OPK's before I got my fertility monitor to help me pinpoint when I Od.
I hope this was helpful! Like I said, I didn't chart for very long because I found it too stressful for me. Good luck though!!