misoop:
I know how upsetting this can be have had the same thinga
on mine. First is your needel in the right way?
With the grove in the front. ( dont mean to insult you)
What kind of bobbin winder do you use and how is the tension onthem?
Take your bobbin inthe case and look across the bobbin at eye level. Is the bobbin even with the edge of the holder?
It should be flat across the back edges even. If not remove
the bobbin,inside the holder as you look into it on the bottom you will see a flat like spring, use a pair of tweesers or your fingernail and lift the spring slightly
testing until it is level with the back edge of the holder.
You might also remove the needle and the needle plate and check to make sure the shuttle is free and clean (as long as you are there you might as well add a drop of oil).
Of course turn your machine off before hand. turn the fly
whell to make sure the oil spreads and there is no lint .
No insult to you but had mine looked at and that took care of the problem. Good luck.