Cruise Control problems of the 2008 Dodge Ram 1500

The cruise control will automatically disengage without pressing button creating dangerous situations on highways.

Had my cruise control set at 70 mph on my Dodge Ram 1500 truck as I was approaching an 18 wheeler I tap my brake to disengage my cruise and it didn't so I tapped it again and same results and there was cars on my left so I had to take the shoulder of the highway I was applying the brakes as hard as I could but I continued to gain speed ( the cruise was stuck and would not disengage) and had to take the shoulder. I continued to gain speed and ran out of shoulder so I had to cut left back to the highway and hit the trailer of the 18 wheeler. It slowed me down and I cut back behind the trailer and started to gain speed. The 2 cars that was to my left had passed so I cut left and turned off the key and began to slide. I slid about 100 feet and into the median. Also the air bags never deployed. My truck was totaled but fortunately there was no injuries other than a few bruises to me and my 2 passengers. There also was no injuries to the driver of the 18 wheeler.