You should definitely consider filing for disability. First, you are now unable to work. Second, there is a cut-off time after your date last worked, after which you will no longer qualify for SS disability. Third, disability is not final. If you get better, you can return to work. Fourth, you may earn up to $1000 a month while on disability and retain your disability benefits and medicare. In addition, if you want to try working full-time and earning more than $1000 a month, you can do so on a trial basis via the ticket to work program, without losing benefits. Fifth, you should not label yourself based on external circumstances, such as being on disability. Just because you are legally 'disabled' does not mean that your soul and spirit are disabled. Only you can define who you are. You are a unique person and only you can determine your true worth and identity. You are one of God's children, and your worth should never be rooted in your ability/disability to do work. You are valuable simply by being alive.
Finally, the rules on CF disability may be changing soon and becoming tougher, so I advise you to file right away. Don't cheat yourself out of needed money because you are ashamed to be considered disabled by some faceless bureaucrat you will never meet, and to whom you are just a bundle of paperwork. Don't act out of fear of your family or friends thinking that you are a failure. If they love you and have an accurate understanding of your finances and the severity of your disease, they will support you. Protect your finances and try to save/invest for the future. You deserve it. If you meet the SS 'medical listing' definition, you should just file yourself, no experience required as your case is a slam-dunk when you meet the medical listing. That is what I did. Alternately, Beth Sufian will file for you for free if you are low income.
I am on disability and do not enjoy it, and want to return to work full time. However, I don't define myself as disabled. I still work part time from home, and see my new full time job as being taking care of my health and enjoying life to the full. I enjoy having the time to read more, take classes and indulge in my many hobbies and interests. I plan on getting better and going back to work in the future, when better medical therapies are available. In the mean time, I am determined to improve my FEV1, get super-fit and stay motivated.
Don't short-change yourself.