I have been using 'ovunow' OPK's which I buy from my ob. I used the last one today and forgot to go and get some more! It is now late in the afternoon on the fri of a longweekend. It is most likely I won't O until after next tues but I would like to be able to check. the chemist has different brands of OPK's (really expensive!)... I just wondererd if anyone knows if it is ok to change brands mid-cycle or is this a bad idea? Thanks