I know how you feel, and sometimes protecting an original idea or intellectual property is difficult. Here are some steps that may help:

Find a qualified attorney. Patent lawyers are used for protecting intellectual property or business ideas and you won't mind spending a bit extra for a good one.

Carefully track the development of you idea in writing. Use a log book to write down every step in order to prove that it was your idea.

Research similar ideas. It sounds like you've done this, so find out if the idea is already patented and does not violate the rights of others.

Keep careful track of how and who you show you idea to.

Hope these help!