Cherry, there is a lady in Ruston that may be able to answer your questions. Call me and I can give you her no.
I would try cleaning the bobbin case (dust it with the little brush that comes with the machine). Then rethread the top and the bobbin. Sometimes I try a new needle too. Just give it a fresh start all the way around. Then do a test stitch on a good solid fabric with a solid stabilizer and see what happens (I had this issue in the beginning and found out is was "user" error with fabric and stabilizing - but as someone said below - your dealer is your friend - mine sure was when this was happening to me).
Cherrysue, How long have you had your machine? Has it had a tune up? If you have been doing a lot of stitching lately, you might want to get a tune up so it will run smoothly. If not, the you need to adjust your bobbin. Does it pull easily from the case? then you need to adjust the case, if it is okay then adjust your bobbin tension from your machine.
Your dealer is the answer! He (or she) can fix these kinds of problems quickly; sometimes, right over the phone.
what I have learned is that if there is a problem on the top of the fabric,it is the bobbin. IF the problem is on the underneath the problem is the machine isn't threaded properly on top. Good luck.