Someone has access to my account

I've been playing SWGOH for a while, and have gotten all the way to ~8.5m gp. Recently I noticed a bunch of small things happening, including my crystals being spent without my doing, my GAC battles being lost, gear being applied to random characters, and even my account leaving the guild it's in. It's incredibly frusturating and I can't progress ingame anymore. 

How do I proceed? Is there a way to unlink the account from everywhere its linked and relink it to secure the account?

Thanks