but hopefully you will not!! Is there a reason you thought if you'd ovulate that it would be before the HCG trigger? The trigger is to give you that last push before the pseudo-ovulation, i.e. egg retrieval.
The other IVFs you refer to, were they are Cooper? I believe it is standard for them to do an u/s just before retrieval. My retrievals elsehwere did not do pre-retrieval transfer; only the day before retrieval.
Hang in there until tomorrow! Best of luck to you!!