I don't know much about the laws regarding this, but as far as finding a cheap or free attorney goes, try a law school. Any decent sized one will have some kind of clinic. You'll get a third year student who's being supervised by someone with a lot of experience and it's usually free or very low cost and you end up with pretty decent representation because the students are out to prove something so they put a lot of effort into things and the supervising attorney has usually seen a lot.
Good luck. I would agree with whoever said not to disclose (unless it ends up being necessary) and if you do so, keep it to a minimum required by law and to the minimum number of people possible.
And do keep a journal recording all these events. You'll need it if you ever end up in some kind of law suit situation. Also make sure you keep records of reviews, notes of praise etc in case they try to use your actual contributions as grounds for dismissal.
And this is probably why you need to speak to an attorney before you disclose anything, but for example the state I live in is an at will state and either party can terminate employment for any reason at any time or without giving a reason. An attorney would know the laws in your state and be able to advise you on proper disclosure.