This is a question that really needs to be fielded by your mentor. (You do have one of those, right?) It's really hard to give a good estimate over a web forum on this kind of thing--it works much better to have an experienced eye who can show you what to look for with both physically and with her changes in behavior.
One think I would strongly recommend, for anyone who is unsure of when their female's most fertile days are is to have progesterone testing done.
