Hate to say it, but that is the name of the game with: supply and demand, and competition. Unfortunately, there was nothing proprietary about your design or your products. However, the one proprietary thing about your products is the quality. Doesn't matter if someone copies your design if the quality of their product is inferior to yours. People will always buy a superior product at some point, or wish they did, and pass that desire on to others.
Instead of being a little fish trying to swim up a big river, and selling your products online, why not try making products to sell locally, same principle as your food truck, and build a name and capital. Then, when you're a bigger fish, then you can start trying to swim upstream and mainstream.
You can make a spoiler for somebody's Camaro, Mustang, or Civic just as easy as you can for a Plymouth
