Up to 40% of those with Sjogren's have negative blood work. If you have significant symptoms (dry eyes/mouth, fatigue, joint pain, etc) then maybe you should consider being worked up for Sjogren's with a Schirmer's test (to assess tear production) and lip biopsy...which is more invasive and should be considered if the Schrimer's is positive and they believe your lung issues are autoimmune related.

About your shortness of breath. Do you get SOB while sitting quietly, or more while exerting? Have they exhausted the cardiac angle?