I'm no expert by any means but I think with OPK tests a faint line doesn't indicate a +/ the line has to be as dark or darker? than the control line for it to be a positive. P.S you make me giggle
Maybebaby is right. You always have some luteinising hormone in your body so you will always get a faint line on an OPK.
The test line needs to be as dark, but preferably darker than the control line to indicate a surge.