Something wrong with my bike???

I can't seem to work out what's wrong with my bike. It just doesn't feel right when I ride. At first I thought it might be that the cone on the hub might be worn away but I've had it checked out and there isn't a problem.

The rims are not dented or damaged and the spokes have all been replaced and trued.

The only other thing I can think of is that on the rear wheel the splines on the hub body and the splines on the cassette cog are worn and this results in a slight wobble whilst moving. Can this be known to be a problem?