OPK help please

So I am new to using opk's...this is my first cycle after my d&c 6/17/15 & I'm only on CD7, but I tested this morning out of curiosity as I dont exactly know what CD to begin testing. I know this is a negative result, but my question is should I continue testing daily now since there is a faint line or should I wait until CD10-12? Is there always a faint line, no matter if you're close to ovulating or not? Or does a line, no matter how faint, mean you're getting close to your LH surge? Any help would be appreciated!