97 Deville Battery keeps dying????????

I recentl purchased a 97 Deville and my brake lights keep coming on when car is parked. I think it has something to do with Alarm. I do not have a clicker to turn alarm on or off. When car sets for more than an hour I have no charge on battery to start car. I have to jump the car and wait about 10-15 minutes befor I remove cable to keep car running. What could be causing this. Someone Please help....

Is it just when the car is parked or are they on all the time?

The brake lights come on and off when car is parked as well as when driving down the road I have been told.. Doesn't make any sense. I have installed a new battery and had the alternator checked. The first full day I had my new battery my car wouldn't start due to no juice coming had to get a jump. Something is draining my battery and I can't figure it out Could it be the Alarm?????Any ideas?

Have you had the brake light switch checked under the brake pedal?