Wow congrats on losing 75lbs that is amazing! I know I need to lose that much and it is nice to have some inspiration!
If you ask questions on the main board more people will see it easier and be able to answer your questions. the other ladies on this board have done more charting than I have but I use the fertility friend website (I don't pay for the VIP, I just do the freebe). You can chart when AF comes and also record your temperature everyday (and anything else you want to track). I find it pretty simple to use.
Here is a link to the ABC's of charting
The ABCs of Basal Body Temperature Charting at the Preconception (Trying to Conceive, TTC, Fertility, Pregnancy Planner) Cubby at StorkNet
Although charting your temp will only tell you when you have ovulated and not tell you before hand. OPK's are great for letting you know a head of time so you can still have time to "make a baby".
Lots of the ladies on here by them on amazon, high quantities for cheap. Unlike me who buys 9 test for $40.
The ladies on here are the most supportive and knowledgeable so I would suggest sticking around.
Good luck