93 sc2 e-brake sensor

Hi, I currently own my saturn sc2 and have add it for 1 and then some, first car by the way. It's help up for me really well. I've had almost zero problems with it and it now has 203,000 on it. Around the time I first got it, the trany was a little sticky if you will, it got jerky or something, but that kink worked its way out. Now I'm having an issue with the e-brake sensor. I know the e-brake is not engaged, because when i'm going 55-60, it doens't decelerate fast at all. When ever i drive less than 20, the light is not on. When I drive between 20-35/40, it turns on or off, and after 40 it stays on. I will be driving 55 and the light will be on, and when i decelerate to about 38, the light turns off. And the e-brake is all the way down. So i'm thouroughly stumped on what this could be. I was also encountering some extensive shaking when driving over 50, but that's gone away, i don't know if that's related or anything. so any help is much appreciated, thanks, Gavin. I live in nw indiana so there is snow and salt, so i don't know if that will be of any aide