I have transient pressure and swelling above left collarbone for about 3 months. Started about 2 weeks after I was hit from behind in motor vehicle accident. No pain associated. I feel like compression in the area but no difficulty swallowing or breathing. Sometimes I feel it above the collarbone, sometimes across base of neck, sometimes higher up on left side of neck. When I massage the area no lumps or bumps are felt. I had chest xray, ekg, blood work all normal. Chiropractic treatments and massage therapy provide temporary relief. Any other ideas?