I really am not surprised that you are having symptoms due to such a daily low dose for three years.
One piece of advice is never, ever take 'normal' 'o.k.' or 'fine' with regard to blood tests results.
If your dose is too low it can cause us even more problems so I would suggest your make a new appointment with your GP saying you don't feel so good. He should also palpate your neck and refer you to an Endocrinologist to diagnose why you have a lump.
When you get a blood test for thyroid hormones, this is the procedure.
The appointment should be at the very earliest and fasting, although you can drink water.
Also leave about 24 hours between your last dose of levo and the test and take it afterwards.
This allows the TSH to be at its highest as that's all GPs take notice of.
Ask your GP (say you have been advised by the NHS Choices for advice on the thyroid gland,) that you need a full thyroid function test (he may not agree but you can have a private one if you can afford it). TSH, T4, T3, Free T4 and Free T3, and antibodies (if you haven't had an antibody test) Vitamin B12, Vit D, iron, ferritin and folate.
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