How unique does my pattern need to be? Can you borrow a stitch pattern from a stitchionairy? Kate Atherley answers these questions and more here.
What is protected with copyright then? Where am I protected?
Now we're getting into international law, and it gets very tricky. Intellectual property (IP) rights are territorial. They only give protection in the countries where they are granted or registered. You can find more information from the British authorities here, or read up what the rules are in your country.