I have a 2003 Monte Carlo SS 3.8 v6 I just bought new headlights to get my lowbeams working again. Lowbeams on drivers side only lasted a week. Checked fuses and bulb both are still working so not sure what the problem could be.

 

If you swap the bulbs between the sides, the driver side is still failed? If so, it sounds like it will take reading some wiring diagrams and testing a few things out to pin point the fault.

 

If it started working suddenly when you put the new bulbs in, it could be something in the harness / wiring closest to the bulb. Id get a multimeter and check plug while you shift it around.