LG, glad to have you here! Your blood tests and cycle length would suggest that O is occurring around day 17... Just like I don't have a good relationship with clomid, I also don't have a good relationship with OPKs! (but that could be down to never actually having ovulated, really ). Can your specialist organise scans and/or blood tests to help you know when to BD? Good luck, in any case!

BW