Transmission not working properly

My vehicle suddenly started slipping out of gear while driving down the road. While driving my RPMs all of a sudden shot through the roof, like my transmission was slipping. Trying to get my car off the road a couple more feet I began pressing on the gas a little bit then my car shifted back to drive, then back to like it was in neutral again. While I was sitting waiting for my ride, I had left the car in drive because it was not moving and all of a sudden it engaged back into drive, only to "slip" again shortly after. My check engine light is not on, my truck is not throwing any codes, when the car is running and I go through all the gears on my shifter (drive, reverse, etc) my truck will allow me to shift through all gears but you can't hear the gears actually engaging at all. I had the transmission fluid drained and filled back up and the issue still continues once my car engine is warmed up to normal temperature. Please help!