I've been feeling tired and achy for a few months now. Biggest issue has been an ache in my left arm that won't go away. A couple of weeks ago I found a tender lump at the bottom of my neck about where my thyroid is (I am already hypothyroid). 

I went to ser the doctor and she said she thought it was soft. What i can feel is absolutely solid but it is at the base if my neck and may have felt in the wrong place?

she did say I also had a swollen lymph node in my left armpit and I wonder if this could be causing the arm pain? 
 

the lump on my neck front was very tender at first and is now less tender. It's firm but not totally solid I guess?
 

Am I going mad? I've asked for an ultrasound.