You could have some kind of malformation or inflammation from your injury causing a build up of cerebral fluid, so when you move it's able to rush past into the spine and make the funky fluid noises. In perfectly healthy people, the flow is controlled by a sort of tonsil, and during movement or laughing/coughing it is able to escape into the spine as well. In people who have a malformation from birth, it can cause all kinds of physical developmental issues like lopsided muscle reactions, scoliosis and such. It also gets worse and worse, not better.

I'm not a doctor, just had a close family member with a malformation there which was corrected with surgery. You should really see a specialist!