normal but not normal

I have a multinodular goiter and now it is very large. It is substernal and so large that my endocrinologist cannot get it on one frame with a sonogeam. I have had all the blood test for hypo and hyperthyroidism. All are normal. I have had all the antiglobulin tests for autoimmune thyroid and those came back negative. I have had a thyroid biopsy but that came back benign. I have all of the symptoms of hypothyroidism; not one is absent. What could be causing this and will a thyroidectomy and subsequent levothyroxine management correct the problem?