Fertility appointment ultrasound

Hi

I tried to find an answer my question but couldn't. So I had my referral appointment to the fertility clinic where I got a internal ultrasound, this was 4 days before expected period. And everything was fine so therefore got my hopes up that there was a huge chance this month as she even said i had a good lining. However AF right on time. When she was looking at my ovaries there was a follicle that was larger than the rest, it wasn't big enough to be a cyst. It was almost like i was ready to ovulate. Has anyone got any information on this or do you think its most likely to be the egg maturing for this cycle I am on now? I'm currently CD3.

Thanks ladies appologise for my essay and a half x