OPK question!

Annie
I have been using OPKs and on CD8 I got an almost positive when I tested in the afternoon, that was the first test I'd taken this cycle. Since then they've been getting weaker again and this evening the line was almost invisible. I'm on CD10 today. 
Never actually saw a positive but is it possible to ovulate so early on in a cycle? My cycles are usually around 26-27 days, with ovulation around CD13. Anyone had this happen? I will continue with the OPKs but just wanted to hear people experiences *impatient!* 😆