If you have a change in circumstances that makes your current child visitation schedule difficult or impossible, you might need to request a child custody modification. In the best of circumstances the other parent will agree to whatever modifications you require. In the worst of circumstances, you may need to go to court.
I just read The Seattle Times' article, "In Washington, there's a low-cost alternative to hiring (or becoming) a lawyer", and I think you might enjoy it, too. You can read the full article here: