I took mine to a bike builder and he did something with a piece of steel rod mounted in the steering bearing hole and a couple of chalk lines on the rear made after a couple of measurements . When you then looked from the rear to the front it became obvious it was out of alignment.
Not much of an answer, but try calling a bike shop if you don't get the answer here. I think it was something I could have done myself.
2nd post: I called him and he indicated it would be very difficult to describe on the phone. Here is his info, he's in Cowichan area. Not that far from you, and it only took a few mins.
Frame check
West Bike 4335 Gerz Fred 250 -748-8465
Turn Lake Cow #18 RR 1 mile flashing light Tansor Rd. Left 1st right ---old rd 2 klm on Right. Fire to far. 10:00-5:00 Sat .