Starting Clomid before AF?

Amanda • 33yo. TTC #1 for 18 months now. Starting IUI journey.
1st cycle of Clomid (50mg) my largest follicle was only 11cm and my Progestrone level was on .6. My OB said I should go ahead and start my 2nd cycle of Clomid and don't need to wait for my period (due next Fri) before starting since I most likely am not ovulating. 
So starting cycle 2 at 100mg this time. Has anyone ever started Clomid before a period like this?