Chevrolet,My truck won’t allow me to change gears even when pressing the clutch. No gears go in at all. Makes it impossible to drive.

I was driving my truck on first gear, I stopped and was about to make a right turn on a corner at a stop sign. I accelerated a lot and my truck started running, but when I tried to change to second gear it didn't allow me to. I turned of the truck and managed to put it in neutral. I pushed it and parked it. I found out that when the truck is off I am able to shift into any gear, including reverse, without stepping on the clutch. When the engine is on I am unable to put it into any gear no matter how deep I step on the clutch. If the truck is off, and I put it into first gear, then turn the