From what I know of Endo, it is very painful and can give you the general crappy feeling but it shouldn't cause joint pain or swelling. Auto-immune issues have been linked to changes in estrogen levels, not sure if Endo affects estrogen levels or not but something to ask!
The chest pain can be from inflammation in the cartilage between your breast bones and ribs and that usually won't show up on x-ray unless its really doing serious damage. This inflammation can be caused from strenuous activity, trauma or an auto-immune issue, like RA or Lupus. I can not inflate my lungs fully the swelling is so bad. It hurts to raise my arms or lift anything. This is a very painful symptom!
Rashes are typical in Lupus but alone, not enough to diagnose Lupus. I am very photosensitive but have never really had rashes before. I have a few moles that are "suspicious" and have an appt scheduled with a dermatologist to take a peek! But that probably has nothing to do with the auto-immune issues!
Not to alarm you but please mention the swollen lymph nodes to the rheumy. Lymphoma can also cause all the symptoms you are describing.
I'd advise you to make a list of ALL your symptoms and approximately when they first started. List what tests you have already had, the allergy tests, thyroid work-up and chest x-rays and other stuff. The doc will want to know how long you are stiff for in the morning, how much activity you can tolerate and what makes your symptoms worse.
I understand being young and feeling VERY OLD!!!! You have time on your side, if this turns out to be any sort of auto-immune illness, with the right treatment, you can avoid many of the problems I'm having! Do NOT be shy with the doc!!!!! You know your body better than anyone else. Just because they have a medical degree, doesn't always make them right! Make your list of symptoms and questions and don't leave until you understand the answers. He may not be able to give you all the answers until he does further testing however, you need to feel that everything is being done to get to the bottom of why you are feeling like this!
-------------------- Taking it one day at a time.....