Hey guys I get it now,
Here's the right code:
$this->db->select('ut.Username, ct.Title, ct.ContentID');
$this->db->from('username_table AS ut, content_table AS ct');
$this->db->where('ut.UserID = ct.UserID');
$query = $this->db->get();
return $query->result_array();
The problem is this line:
$query = $this->db->get('content_table');
Because I call this table it adds from the actual SELECT that I already made.