How can I track my iMessage history?

iMessage history cannot be tracked. iMessage uses data, so it is the same as sending an email. It just uses a data package. What you used to see in your Verizon bill was SMS, which is texting, controlled by the cellular carrier.

I'm not sure exactly what you mean by "track". Only SMS (green) messages will appear in your carrier history. iMessages (Blue) will not and never have appeared on your carrier's billing history.