It is not an ex-parte order, because it is not an order, just a Motion for an order. You can file a written resistance, and state your reasons, but your consent is not needed - if the Court finds there is a cause to grant your ex's Motion, it will grant it.
He is also not required to personally serve you notice of his Motion - he can mail or email it to you. The only thing not clear from your post is when did he file it? If he filed it the same day, or a couple days, before you saw it on IA Courts Online, then there's a chance you just have not received it yet. Also, if you have an attorney on record, then he is required to send your attorney notice, but not you.
Lastly, if this is an electronic case (on EDMS), then the EDMS notifications satisfy the notice requirement.