Maybe check to be sure you're not using the auto dimming bright lights? I've noticed that they don't always dim right away depending on where the oncoming traffic is in relation to the lane I'm in.
Another thing you can try is to drive down a dark street and watch where your headlights are hitting the cars parked along the street. I'm pretty sure my lights hit just below where a driver's head would be, so they shouldn't blind anyone.
The other possibility is that people are signaling you to say, "hey, nice truck!" >