1998 ford mustang v6 rear end problem

I was driving home yesterday and my rear end started making a big loud noise and my motor was going up in rpms and it was vibrating the car I got about another mile down the road and it was like the driveshaft was hitting the floor board I pulled over and the back wheels locked up I set there with the motor off I put it in neutral and tried to roll it backwards but it was stuck I started the car back up and put it in drive it pulls forward but when you back up it flops like its in a bind you can drive it in forward but it still thumps and makes a clacking sound but in reverse it don't want to move at all I got it home and jacked it up I turned the driver side wheel and looked at the driveshaft it looks like its got a lot of play I couldn't really tell a whole lot about it where it was getting dark does anybody have any idea what could have caused this?