Help :(

[MerryBerryru]

So a while ago my friend somehow linked our accounts. When I play songs it shows up on his Facebook page, and we can't be logged in together at the same time. When I log in (with my information) his picture and information show at the top, right corner. When I click on his account information, my account information shows up. When his friends join, I get an email.

How can we undo this??