Your symptoms sounds just like anxiety, minus the swollen tonsil that might have something to do with a previous cold. Sometimes lymph nodes remain swollen after inflammation, but they no longer signify any illness. A tonsil swollen for over a year is very likely that. I have a swollen tonsil on the right for many years too.
Now - the thyroid cancer - I really doubt you have that. If it was big enough to give you swallowing difficulty, you would be able to feel it or even see it. You can always check for thyroid nodules because the thyroid is a thin, small gland and you would feel a cancer quite easily. I'm sure you know where your thyroid is, between the middle of the neck & above the pit of the neck, just feel it with your fingers. Easy to do.
The lump in throat, throat fullness sensation is EXTREMELY common with anxiety, I have it as well and I worried about my thyroid too.
The headaches, ear fullness, throat tightness, neck stiffness are caused by tension, they are related to anxiety. I have the exact same symptoms. They suck.
The chest pain again is another common symptom of anxiety and muscular tension. I've had that as well, mine was to the right of the sternum and sometimes it felt deep inside, other times just under the ribs. It was like a dull pain/discomfort and it was almost constant! I've had it for 2 months before I managed to relax enough for it to go away. It still bothers me sometimes when I get tense.
I feel ill as well. Like I have the flu.
I've been to many doctors and had many investigations done. They all sent me home and told me I have anxiety and possibly depression as well. They told me to find an occupation to keep myself busy and stop focusing on myself and my body. I guess I will pass on this advice to you... your symptoms absolutely sound like textbook case anxiety.