Hello. You can be born with it, or you can develop it in later years. Very common for teenage girls to develop it, and it's onset can be quite insidious (there is a push to screen teenage girls for this is schools). it's unlikely to go as it's a bony curvature of the spine (as in your case is often more obvious when your scapula (shoulder blade) sticks out a bit more on one side). Any deformity of the spine affects your rib movements, which is why breathing becomes more difficult. Ask your doctor to refer you to a physio for advice on how to manage your condition.