I am so confused!!!!

Ok so I started Clomid cycle day 4 (100mg) for 5 days. My Dr put me back on another cycle of Clomid on cycle day 12. Today (cycle day 15) I had an appointment to check my follicles and pick up a prescription for a trigger shot I was supposed to do tonight, so we could inseminate on Monday, but when I went in, my follicle that measured a 16 on cd12 was no longer there. Which means I had already ovulated. He checked my urine and the opk was positive so we went ahead and did the insemination today. Do any of you feel like I could've missed my window? Or am I just freaking out?!