Okay, sounds like your clutch(pulley) isn't disengaging.
Torque converters have centrifugal weights inside them, and the faster the crankshaft spins, the weights sling out and push the moveable pulley, which tightens up the belt, it sounds like your weights or spring, isn't fully releasing.
Usually you have to take it apart, and clean it, and lube it. Or buy a new one.