Clomid missed ovulation?

Hi everyone. I am currently on my 2nd round of 50mg clomid after having a positive ovulation last round but BFN. I had my follicle scan yesterday on day 12 which was a few days late due to day 10 falling on a Sunday and then bank holiday Monday. My scan yesterday showed I had 2 follicles measuring 23mm each. I have been using OPKs since day 10 and had negatives and still a firm negative this morning. Is it possible I have ovulated early this month and the scan has missed it? The doctor did say if ovulation had already occurred the scan would show as a collapsing follicle which it didn't but not sure they can actually tell. Follicles will be 24-25mm today so if I was still to ovulate should the OPKs be showing something by now? Clear blue Digital also negative. Thanks so much x