Hiya. We all carry a small amount of LH surge in our bodies even when we are NO where near ovulation.
You will get a very faint line on a opk ( ALL THE TIME ) even if your not in your fertile phase, it's only classed as positive when its almost the same as the control line or darker than. Keep testing hun, sometimes you can miss your surge its that easy to do, unless you test twice or three times a day ( like i do ). Testing onec isnt reliable as you will miss your surge, i test from 3pm then 7pm & 10pm that way i never miss my surge. I use internet opk's ( one step ) & they are 100% reliable for me, always get my surge on them.
Goodluck x