Thanks Hollye9188 and TwoMums.
Re OPKs, my understanding is that they detect the LH surge and that clomid block oestrogen therefore increasing fsh. i vaguely know that fsh levels are related to the timing of the LH surge but i cannot work out how the lh surge would be blocked or whatever to stop a +opk. Anyway any more ideas very welcome, otherwise i will ask my dr on tues.

Re insemination timing.... I have a relatively long follicular phase and usually ovulate between CD 17 and CD21, have a 27-30 day cycle with a 9-11 day luteal phase. I don't know (and maybe someone else can tell me) whether having clomid (CD 3-7) is likely to shorten the follicular phase and therefore make ovulation earlier? I make have to chat with our donor re doing more inseminations over a longer time if we are not going to be able to rely on opks. Will also ask dr re trigger shot, thanks twomums for that... Does trigger shot need to come from fs or do general obstetricians prescribe them??? thanks again, girldoc