I am sorry for your trouble, here is what i do:re-thread, next check for any fuzz or lent in any of the tensions (smallest piece can cause biggest problems for me) and even the bobbin, one of the thread guides on my machine has a small plastic tube on it and if it jumps off no more sewing.Check for a burr in throat-plate or bobbin case.You may have checked all this . I hope things start working better, it is not fun when you have so much trouble.Good luck.