Hello Sue,
Fisrt off it sounds like a major tension problem so check that first, if you are happy with the tensions and made sure you have threaded the machine properly then you may need to retime the machine which you can do providing it is not a two piece split body machine, if you need timing instructions I can attach them if you e-mail me but let me know if you have a drop in bobbin machine or front or side loading machine.
Ken
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