Truck feels like its pulling a trailer?

Have you checked your brakes? Does the engine sound normal? Do you notice any difference in takeoff performance when you put the shifter in "1"? Is there a trailer hitched to your truck?

I'm hoping it's that last one.

Could have jammed something on E-brake line.

could be a bad knock sensor sending the ecm into fail safe mode.

After it happened I parked the truck. I went out to start it, started it up and the O/D light on the dash was blinking. I hit the O/D button, it stopped blinking, and it ran fine. Not sure whats up with that.

you could have just gotten snow snow/ice/water in the electrical connector on the transmission.