2006 Dodge Ram Truck jerks while driving as if someone is p

My truck started jerking - sometimes it is violent sometime just a small jerk, while I am driving. We have had it in the shop four times and spent nearly 2000 dollars. This dealer just seems to be guessing at the problem. We have had it tuned up, a 600 dollar valve put in the transmission, a computer chip, nothing has worked. In fact it gets worse and worse. Today the check engine light came on - its the first time that happened.

Any ideas on what the problem might be? Anyone had a similar problem? What was your solution?