I would need a little more information, 1) why did you replace the headlight switch in the 1st place?
2) I assume the headlights weren't working, there could be a power supply or ground supply problem in the circuit. 3) Does the headlight switch fix your original problem then it goes out in a short period of time? A lot of the time it turns out to be a connector issue more so than a short somewhere. You really need to get a wiring diagram and start checking the circuit with DVOM and check continuity with the wires. Sometimes there's a body control module that controls the exterior lighting that could be a issue too. But the first thing you need to do is get a wiring diagram. You could do a seach on the internet & possibly find it that way. But to tell you where the short is? Well, its just not that easy and I'm sure if I had the answer for you- I'd go to work finding missing children. One more thing- if the circuit tests out good- you may want to question the quality of headlight switches you've bought. It's been our experience to not assume electrical parts from "discount auto suppliers" to be reliable parts.