The Washington Dept. of Labor and Industries has some good info on this topic.
http://www.lni.wa.gov/WorkplaceRights/Wages/Overtime/Exemptions/default.asp
Retail employees are generally entitled to overtime. But there are exceptions made for employees that earn a commission on their sales. If you generally earn over 1.5 times the minimum wage when you include your commissions (min. wage in WA is $8.55 per hour) then you are likely being compensated correctly.
The other big exemption is white collar workers but if you are actually white collar you probably wouldn't consider yourself in a "retail" position.
I'm not a lawyer, this isn't legal advice. You should talk to a lawyer or at least call WA DOLI and inquire about your specific circumstances. Their employee hotline can be reached at 1-888-811-5974