Prevailing wage and weekly hours confusion

So im gonna jump right into this, So my boss and our newish secretary at his small service company (3 of us) have been keeping track of my hours in a odd way that makes me feel like I may be getting cheated of of proper pay. We’re based out of Oregon but do tons of work in Washington state and any public work done by contractors in WA usually requires they pay there employees (me) Washington’s prevailing wage rate for our trade (heating equipment mechanics). So today I worked at a fire station from 9:30am-5:30pm (7 1/2 hrs) with a 30 minute lunch but my total hours worked for the whole day was 8am-9:15pm (13 1/4 hrs) total. So he’s been having me break my hours into something like this ( 5.25 hrs reg) (7 1/2 prev.) he claims because my reg rate that day isn’t over 8 I don’t get any OT. But what is messing with my head is even though I worked 13.25 hours today it doesn’t seem right. Because with his logic and for easy math, Say I work 7 hrs reg rate and 7 hrs prevailing everyday for a whole pay period. He wants to do pay roll as 7 hrs REG x 5 wrkdays = 35reg hrs and 7 hrs PREV x 5 wrkdays = 35 prev hrs = 70hrs in 1 week. Double that and that’s a pay period of 140 hrs. With his logic I shouldn’t see a penny of OT because in both weeks I would never hit over 40hrs of reg rate despite working 14 hr days everyday for 5 days each week. In Oregon I believe it’s another over 40 is OT but he’s adamant I’m wrong. Does this sound right ? Or am I just a dummy?