If currently you can't legally use his name you can always file a petition for a name change. You will probably have to file a notice in the paper for four weeks. Seek out an attorney in your area, it should not cost to much to change your legal name.
This is general information not to be relied upon and no attorney client priviledge exists.
King County District Court has a great info page about name changes (see link below). It's pretty simple for an adult to legally change her own name, and all the forms you need are available on that page.
Legally, in WA, a person can start using any name the person likes as long as using the new name is not for an unlawful purpose (such as deceiving creditors). In WA, a person does not need a court order to have a legal name change.
Practically speaking, creditors, government offices, and other offices like to have documents to put into their files to connect the new name with the old name. So, those offices likely would demand that you get a court order to change your name.
Changing names in WA is very simple. It can be done within a day if the person shows up in court early enough to get on the court's calendar for the day. Unlike many other states, there is no requirement to publish the name change in advance. The fees are about $150 in most courts.
Each office likely wants a certified copy of the court order changing your name. So, you should budget a few dollars into the cost for each office you intend to notify of your name change.