In light of some of the lawyer-equals-adversarial comments above, I should clarify: definitely don't tackle your partners with a lawyer. What I'm suggesting is hire a lawyer you like / you get through a trusted recommendation to read things from your point of view, then give you advice at the present time.

A good lawyer will present things as they stand, but also let you know where the line exists between asking for what is fair and pressing your case more strongly / becoming more adversarial. They will leave the choices to you, but they will inform you well of the spectrum of choices that you have.