I’m An Artist And Make A Living Selling Products With My Designs. How Can I Best Protect Myself Against Infringement?

I make things like enamel pins, jewelry, stickers, etc. I’ve had some of my designs stolen and copied in the past and it’s devastating. There’s nothing I can really do about it now (the companies that copied me are overseas) so instead I’m thinking about the future. What are the best steps I can take to protect myself against this happening again?

To be as clear as possible about the situation: I create artwork and then translate that artwork into physical products. I’m in the US. I know that the actions I can take against overseas companies stealing my artwork are very limited so I’m trying to do preemptive damage control.