Gabby,
Just so you know, most adoption attorneys will do a free initial consult with a woman considering making an adoption plan. Below is a link to a listing of adoption attorneys in the US:
American Academy of Adoption Attorneys - Home
You should know your rights, especially when your family is thinking of asserting their rights. It will also be helpful if you do decide to make an adoption plan in the future. Just make sure that any attorney you consult with is not also the attorney that is speaking with your mom or the potential adoptive couple.
I'm pretty sure that legally you are able to make any decision regardless of what your parents desire and it doesn't matter if you are a minor -- but get that from the lawyer.
M