What Causes Popping Of Head Leading To Dizziness?

hi. i was rear ended a month ago and have severe whiplash and c-5 bulging disk and a pinched nerve..i get really dizzy spells almost all day especially at night. my mri showed the bulging disk and spasms. i have a distinct pop everytime i tilt my head back and it makes the dizziness worse.i also get vertigo and it's hard to concentrate. what is the cause of this popping and what can i do. ive been going to physical therapy for three weeks and see no difference in symptoms.. My doctor can't find the reason for the popping.