What Causes Delayed Menstruation While On TTC Treatment?

I am currently ttc. I took provera to induce my period and clomid to induce ovulation. I used clearblue advanced opk and had high levels for five days and received a peak reading on cd 19. I started testing with hpt at 10dpo. Yesterday was 15dpo and all have been negative. If I ovulated, why haven t I started my period yet? I ve put a call into my obgyn but they re referring me to an RE. I am going crazy needing answers before then! Please help and thank you in advance!