Wow, that is quite the drop! Are you taking your temps everyday at the same time without interuption to go to the bathroom? You need to take the temp at the same time every morning and hopefully, you won't wake up to go to the bathroom within three hrs of taking your temp. You probably know that already, though.
I would disgard your first four temps. Normally I would agree with Kelly about not starting to take your temps until cd6, but since you O very early, I would suggest that you start temping on cd5 of your cycle.

However, I don't know if this is the norm for you so I would probably keep temping everyday for another cycle or two but if your temps are super high like this cycle, disgard the first four temps and from then on, don't temp until cd5.
HTH!