Enlarged Thymus, please help

In the past Year and a half I've had 3 CT scans. March 2010- 3.1 x 2.0cm, May 2010-3.3 x 2.1cm, August 2011- 3.8 x 2.4cm...last blood test ESRxCYT- 1(low), ALK PHO- 49(low),AST-17(low),ALT-13(low), TSH-6.37(high)

Symptoms- blurry vision,severe limb weakness,fatigue gets worse in heat or bright sunny days, droopy left eye, chest pain, shortness of breath. Physical activity makes it worse but rest improves my symptoms. Enlarged thymus or Thymoma

My doc says its nothing to get excited about but I've had these symptoms for 6 years and until the Thymoma I thought the limb weakness came from a botched hernia repair. Is a Thymoma cancer? My doc says its nothing to worry about and that a Thymoma is just a word that means enlarged Thymus. What should i do? Does it sound like gravis? Cause after all the research I've done especially with the enlarged Thymus it sounds right to me.