Opks.. When to use and which kind.

So I recently had a ruptured ectopic pregnancy on 1/3/14 & lost my baby at 6weeks and also lost my right tube & ovary. Currently me and DH are waiting on AF to start so we can start TTC again. I'm thinking of using opks this go around.. Can any of you ladies recommend a good brand? Should I get them offline?? Also, what CD do you start using them and for how long?? Help please!! :(