Brake lights not working properly

Hi im new to this AF, been reading these for a couple days and thought why not ask my ?'s. my ? is about my brake lights not working as they should be.
I press on the pedal and they flicker on but as I press lower they tend to turn of then turn back on when at a complete stop but not all the times they may turn off completely at a stop. Anyone have any clue what could be wrong?

Need to know what year, model, etc. Also need to know if this is happening to the third brake light also?

Check your brake light switch.

Its a '99 not sure what model as it does not have any emblems on it at all but im 90% sure its the LT model 4 dr 5.7 liter and does not have a third brake light

Your Tahoe would be the 1st I know of that doesn't have a center high mounted (third) brake light installed. As "tailight" posted, check the switch. It's located on the brake pedal.

Well it doesnt have a third brake light because it was removed and smoothed out. One question about the brake switch, how often does it burn out? Reason for asking i had it replaced about a year ago, is that common? Also im looking to replace the brake rotors to performance rotors, brake pads and im also searching for a drop kit for a low but smooth ride.....do you have any advice on what brand for best performance and not too much out the wallet if you know what i mean?

Switches can go bad at any time. Preformance parts you get what you pay for. As the quality goes so does the price.

I replaced mine and it went bad after a few months. I got a cheap one at a parts store the first time, so I went and got one from the Chevy dealer the second time. Mine went bad when I was moving my cars around in the drive way to get my Tahoe out for a trip. I parked half out in the street and moved my other car and when I came back to move the Tahoe it would not shift out of park. If it does go all the way bad and won't let you shift out of park, you can switch the key 1 notch and shift into nutral and than start it and switch into drive. Thanks to this forum for that trick and it helped me get it out of the street. If you get the break switch make sure you get the tab that holds it on while you are there.