Under the federal Fair Labor Standards Act, hours in excess of forty per week must be compensated at a rate of 1.5 times the regular hourly rate. Of course, as many are aware, this only applies to "non-exempt" employees, who are not "executives", "professionals" or "administrators", or who do not fit into another specified category of exemption. Washington may have similar provisions in state law; I do not know as I am not admitted to practice there. You need to present this to a plaintiff-oriented employment lawyer in your state. If you are eligible to recover damages, those damages might be doubled under the law, and you will also be able to seek attorneys' fees, which is critical.
I AM licensed to practice in Washington State, so I will supplement what the previous poster said.
As to your lost vacation time,you can't do much about that unless you have a written contract of some sort which provides for time off. The employer is not obligated to give you time off otherwise.
As to working overtime without pay, it is not legal for the employer to have you do that (whether willingly or under duress) unless you are an exempt employee. Many employers believe that by paying you a salary, they "turn you into" an exempt employee.This is not correct. The Washington Dept of Labor & Industries web site has helpful information about who is and who is not an exempt employee.
If you are not an exempt employee, or if you are not sure, you may want to consult with an employment law attorney. Keep careful track of the hours you work. It is true that in Washington State, your employer may be liable for double damages for unpaid wages and for attorney's fees. That would most likely to be something you would pursue AFTER you have found another job. It isn't fair, but it is true, that suing your employer makes daily life at the workplace awkward, and also makes other employers nervous about hiring you.