Auto immune diseases have nothing to do with age. I am almost 70 but was very fit when I got sick 5 years ago and wound up a quadriplegic. These diseases can hit anyone at any age.
It is more difficult for a young person and I think it was easier for me to cope with the possibility of being disabled and coping with an incurable disease than for some your age.
See your doctor about your new symptoms and focus on getting your immune system under control. Once that is done (which is not always easy) then you can put your life back together again. At your age with early diagnosis and aggressive treatment you should be able to resume a normal life. And if not, redifine your normal and make the best of it. There is much to be optimistic about new treatments and cures.
Hang in there and forget the age thing.
MCTD (lupus, scleroderma, polymyositis). Diagnosed 2005. Kidney, liver, GI tract, dysphagia, raynauds, Barretts esophagus, quadriplegic in 2005. Recovered and now active in skiing, tai, chi, hiking, golf. Meds: prednisone 2.5mg, imuran 25mg, amlodipine, benazapril, omeprazole, potassium, folic acid, vitamins, maxide and various supplements and vitamins.
Remain optimistic and you can overcome the odds.