Cross Progression put me to level 4

Heya,

By 'merging' your accounts, do you mean you had unlinked those platform accounts and linked them to the same EA account? (And how recently did you do this?)
All Account Progress is stored on the EA Account, not any platform accounts connected to it. (e.g., Steam, Xbox, Playstation)

If your platform accounts were linked to different EA Accounts, then that would mean your progress is spread across those EA Accounts, and cannot be merged; as Cross Progression was meant to allow access to progress between platform accounts on a singular EA Account.

What I've seen happen, is that when users play on a new platform (Usually on console), rather than linking it to the same EA account, they make a completely new one without knowing, resulting in this.
The EA Account that those platform accounts were unlinked from, should still have all your progress (Packs, Coins, Cosmetics, etc)
Relinking your platform accounts back to the EA account they were linked to originally, should make you able to access said content on those accounts again.