1Bad54,
It could be your headlight switch, but my guess is that it's a wiring issue on the headlight side of the switch.
I'm not clear on how this is wired. If you have installed a headlight relay, the dash switch would only power the relay. What is the fuse protecting that keeps popping.
Without knowing how you have wired and fused your truck, I would suggest doing a wire search starting at each headlight as you travel back toward the relay or dimmer switch.
The problem appears to be intermittent, which points toward a pinched wire or flopping connection. Arm yourself with some fuses, and with the truck parked in the driveway, try to make it blow a fuse by wiggling and pulling wires in a methodical fashion...flush that gremlin out so to speak. Good luck.
Stuart
