First of all welcome to the QB from SE Michigan. This problem sounds like a machine issue. I would start there. Check your bobbin case and panel to be sure there are no threads of dust collected in the bobbin case and in back of it. Check your tension. It also sounds like the timing may be off just a little. If you are getting a birds nest of threads to the back side check your tension and rethread your machine. I don't know what you mean by "spiral". We have a whole lot of machine enthusiast here that may be able to help you a great deal. What I shared here are just some of the basics. Again welcome to the QB.