Flashing brake light

The emergency brake system had locked up a few months ago. I disconnected the battery and it disengaged. The problem now is that the brake light comes on and flashes. It seems to have also drained my battery somehow. I have driven it and after about 1/2 hour the light goes off and all is fine. The car starts fine. But, after a few hours, I have to jump the battery to start it and the light comes back on. All I can think of is now, not only is the emergency brake system not working properly but it seems to also be draining my battery. Not sure what to think and don't want to be taken advantage of at the dealership. Also, I have had pretty much problems with the brakes. The car has only 21,000 miles and I had to replace the back brakes. Now, the front brake (specifically the passenger side) is making a noise and there is excessive brake dust. I know this is extra information but, I thought I should mention this. Thank you for any advice.