I think just a chest Xray is not enough. Sarcoidosis can occur anywhere in the body.

You also have to get a firm diagnosis...because Vit D is contraindicated with sarcoidosis. If you get a test run and you are high without using supplements, that would be indicative too.

I've always had an mildly elevated ESR, but it never panned out with further autoimmune testing. Some people just have this, in the mild form. ( I have osteoarthritis, and my doctor thinks this is what raises the ESR).

Since you have periods of remission, I'd explore a viral cause.
The Herpes viruses do this, activate and sleep. You can have blood work showing antibody titres... and if high, perhaps a trial of antiviral will help you. You CAN have shingles pain, without vesicles. This virus activates in the presence of arginine, so if you consume high arginine foods, without balancing with lysine, you can activate Herpes.
http://www.herpes.com/Nutrition.shtml

Try some lysine daily ...starting at about 2 grams, and see what happens for you. If you start feeling better within a week, that would point you to viral testing. The Herpes family of viruses are very sneaky...hard to identify when they activate sometimes.