The World Health Organization states that more than one billion people in the world live with some form of disability or ongoing illness. The range of what is recognized as "disability" is quite broad. It's often said that one in five Australians lives with some sort of disability at some point in their lives.
Some of us start out with it, some of us acquire it later. Disability can be transitory and unpredictable. Identifying as living with disability, either openly or simply to yourself, is another process again. For some this is a political standpoint, for others it's a recognition of the additional negative complexity disability brings to their lives.
You may struggle with the issue of having a disability. Some people describe a sort of 'coming out' process when they disclose disabilities which are not visible or immediately apparent.