The flashers quit working?

1989 Oldsmobile Delta 88 3.8 liter mileage: 173,000. The flashers on my car had quit working. I replaced the flasher under the dash and they worked again. Then the brake lights started to stay on some times after driving. I was going to change the brake light switch, but then the lights quit staying on all on their own. As soon as they quit staying on, the turn signals stopped working again. I then replaced the flasher under the dash again but this time that was not the problem; they still do not work but the brake lights work with no problem.