Hey believe, my RE said ultrasound was a lot better than OPKs, as u/s will give you a definite and let them know exactly how Clomid is affecting you. They measure the follicles and based on that they time your trigger shot. I went in for my first sono on CD 12, then again CD14 and CD15 , on CD15 they said to do the trigger shot and I had back to back IUIs CD16 and CD17. The only thing about not doing U/S is that OPKs are cheaper and you don't have to go in for as many sonos. I wonder if the first cycle they don't have patients come in as much... and if it doesn't work the first time then do ultrasounds?