@Charlie74 - how frustrating for you. Is there a point were too much estrogen can have a negative effect on your lining? The only reason I throw this out there is that on my first cycle my lining was 14mm just prior to EPU (my FS described it as a luscious triple stripe) and then in my subsequent two cycles it had got to 8.4 or something like that - my FS has commented that my lining hasn't gotten that thick despite the high estrogen levels ( no more luscious comments!) - in those last two cycles my estrogen levels were really high around 14,000 whereas on the first cycle my level was 8000 or 9000 ( with a similar number of follicles). So my lining was best on the cycle with the lower estrogen. I know estrogen is only one part of the recipe however and it could just be coincidence.