just want to add a quick question- how long does the surge last? ie if there is a positive test one day, will it only be positive that one day in the cycle?
I ask because I have been using OPKs this month, and I was at my mum's place and left the tests at home...so I missed two days...all the days before that were negative..DH and I DTD just in case on one of those days I didn't test in between, then last night when home I did a test and got a positive...so I assume that is my surge? I just wondered had I tested the day before, if it would have been positive too. I suppose every woman's surge time differs.

In the past, I've used them, and stopped once I saw the surge, so I wouldn't know if there still would've been a positive test the next day. Since then, I've been going through IVF...so the need for OPKs has gone...but we are trying naturally this month and next, before we resume IVF.