first off - that bit about opk's with fmu is crap. i have been using opk's now for over a year and i dont get a positive with fmu unless it is a postive! what brand are you using? i use either CBE or First Response. remember, there is ALWAYS lh in your urine... but until it surges you wont get a positive no matter what pee you use. believe you me, i have used every pee possible
secondly, i get 3 days of positives every month. some people only get one day, some people get more. i start to bd after it starts to get darker and keep going thru my last positive to when it starts to get lighter.
i know opk's can be a pain, but they really can be a great tool!