What Causes Tightness In Chest And Swollen Neck?

So I had chest tightness that lasted about two weeks before it subsided. Now my neck feels swollen whenever I lay down for awhile. I've been tired during the days even after a full nights rest. I'm worried i may have sleep apnea.. Any thoughts? Btw I'm 21 and in good shape. Never had any problems like this before so I'm really worried. Doctors don't know what's wrong so some input would be reassuring. Thanks in advance.