EDIT: Looks like I accidentally changed number of values for this field to 1 - it should be Unlimited. It's working now, thanks everyone.
I don't know what I did but I noticed that all (except the first one) body field data in all the nodes disappeared - they're not even available in editor.
All the data is still in DB (in field_data_body table) but it's not showing on website.
I have no idea how to fix this, has anyone had the same problem?