My bobbin cotton wraps around the bobbin holder...

Question

I have tried cleaning out the bobbin area and rethreading, but everytime the cotton continues to wrap around and around the bobbin holder in the machine, causing the machine to jam. How do I fix this?My machine was working perfectly then suddenly it jammed in the bobbin. I cleaned it all out, put in a new needle in case it had bent and now it wont work properly - jams every time