First, glad you're OK and nothing serious was damaged.

Yeah, if I'm turning left, I move far left in the left turn lane. If I'm at a light that doesn't trigger for bikes, I try to position myself as best I can to try anyway, but if a car comes up behind me, I scootch forward into the crosswalk a little so the car behind me can get up on the sensor.

In a combo straight/turn lane I'd signal. But if as you said you thought it was a turn only lane, I probably would not have signalled (but I would have been on the left).