My truck Jerks only in low gear?

2000 GMC Sanoma. We decided to take it on our summer road trip. Everything was fine til we hit DC traffic. The truck would jerk in low gear in the touch and go's like I wasn't giving it enough gas, but when we cleared the traffic it ran fine....The RPMs were a little high running between 2 and 3. We stopped to fill up with gas and right when we left the gas station the check engine light came on. Anyway we made it to our first destination and I took the truck in to get it checked out....turns out the tranny fluid was "bone dry" and the tranny would go eventually, but there was no telling how long I had been driving it like that..... After he put the fuid in it the engine light went off and the RPMs went back to normal.....so is my tranny on borrowed time or did I just get lucky?