messes on the bottom usually reflect problems on the top and vice versa. pull on the thread before it goes thru the needle eye. compare the tension with pulling up the bobbin thread. they should be roughly equal if youre using the same thread size. My guess is the top tension, isn't right. pull the disc out a little and look in the path w a flashlight. dental floss can retrieve thread bitd. or u msy nedd to take it apart and clean it.