I had u/s on cd 3 and there were many small potential follies, but no dominant follicle. On cd 9 my RE was able to see a maturing follie on my left ovary, but I do not remember the size. I wish I did. I'm NOT on clomid this cycle, so it is natural. But I'm an early o'er. I usually ovulate as early as cd 11 and as late as cd 13. I think one time since I have been ttc, I had a 28 day cycle, and I never remember having one longer than that.
I think the later you o, the later you would be able to see it on u/s.
not always, but I have never had an u/S without the stim meds. even after all those it took almost 12 days of meds before my follicles matured. but like cycle day 3 there was nothing, cycle day 8 they were there but small. hope this helps.