I went to invent help with me invention and had a book made so i could get in made but they wanted too much money. However 5 years later I see my invention for sell. I have a letter the day I came up the with idea and a drawing of it. Then I had a book with it made at inventhelp. Is that proof that it is my invention?
If you didn't patent it and, and the people producing the product didn't patent it, I'm not aware of any action you would be able to take.
Patents are distinct from copyright, where the creator's rights are inherent even if they didn't formally copyright the IP, so long as they can prove authorship. (In the old days, before electronic filing, it was recommended people mail themselves their manuscripts and keep the envelope sealed;)
Unfortunately, even if they did steal the idea and patent it, you'd have to launch a suit to contest and invalidate the patent, which would be a protracted process and expensive. In this scenario, it's possible you could approach the manufacturers for some type of settlement.
In 2013, the US law changed from "first to invent" to "first to file". But even before the change in the law, "first to invent" dealt largely with the precedence of the original inventor in the case of competing claims in a situation where multiple parties have filed separate applications.