Dancing requires muscle groups to be used in isolation in a way which is generally unnecessary in normal life. It's not that you're lacking flexibility - this is not likely to be a problem - it's the brain and neuro-transmitter system that needs to be educated so you control the muscles correctly.
A previous reply has made sensible suggestions - basically you must learn to move in a certain way.
My advice - learn one thing at a time, and start SLOOOOWWWLY so you have time to think about what's happening. work at it every day on your own in front of a mirror if you can.
i used to have a lot of trouble with my right shoulder in ballroom (it would raise up at certain points). I practiced dancing around at home in front of a mirror holding a weight (actually a loudspeaker!!) against me with my right arm. It worked! I got used to doing the moves with my shoulder DOWN.
The learning centre used to have something on hip movements - it had good practice routines.
So - work on the movements that give you problems and they will improve.