So with opk's does the test line have to be darker than the control line to be a +?? (i only used them once or twice)
If you were to test every day from end of af would it start like nothing, then get a faint line that gradually gets darker and the darkest would be O day then become lighter again after O?? If so i reckon you should take the + out for day 18 cause if this was after you actually O'd FF wont give you a coverline yet. KWIM? still keep a note on your chart notes though.
What was your CM on day 15? was this drying up then??
It's such a mind wrencher this ttc lark isn't it, you are so close to 2 dates there for O, have you added a day or 2's higher temps in and see what FF does? also try changing the type of monitoring its set as, i can't remember what its called cause i haven't really used it in ages.
at least withthe opk getting lighter you know you more than likely O'd which is great and it definately looks like it frm the way your chart is going, if you have many left do another in a couple of days then you'll be able to use them again towards the end to see if you statrt getting another line before you use a hpt
best of luck (((bundles of babydust)) for you