Feel swaying sensation and dizziness and 24/7 mild unsteadiness while walking more than 15 minutes or lying down or sittingfrom 8 years . is it dangerous?

Is what dangerous?: There is no way to know whether "it" is dangerous without knowing what "it" is. The fact that you've had "it" from 8 years and are still alive suggests that "it" isn't dangerous in the sense of being fatal, but that is all that can be stated based on your post. The doctor who diagnoses "it" will be able to tell you if "it" is "dangerous."