When do I start testing for ovulation?

Anna • Married since 09/09. We have a beautiful son, born on 2/11/13 at 36 wks 3 days. Ttc#2 since June 2014. CP 10/19/14 :`(.
I had a chemical pregnancy and I am ready to start trying right away! Is it too soon to test for ovulation? I am currently cd 5. I still find opk confusing-