1st round of Clomid

I am 43 and ttc on my 1st round of Clomid. My doctor tracked and confirmed ovulation on cd13. It was the most painful ovulation I ever experienced. I also had implantation bleeding on 11dpo. Now after the longest TWW I am two days late for af. Have been taking pregnancy tests from 13dpo until 15dpo. Got a BFN every time. I have always had regular 27 day cycle until this time. Is it Clomid? Has anyone else experienced this? If so, what was the outcome?